:sparkles: Implement Page bundling and image handling

This commit is not the smallest in Hugo's history.

Some hightlights include:

* Page bundles (for complete articles, keeping images and content together etc.).
* Bundled images can be processed in as many versions/sizes as you need with the three methods `Resize`, `Fill` and `Fit`.
* Processed images are cached inside `resources/_gen/images` (default) in your project.
* Symbolic links (both files and dirs) are now allowed anywhere inside /content
* A new table based build summary
* The "Total in nn ms" now reports the total including the handling of the files inside /static. So if it now reports more than you're used to, it is just **more real** and probably faster than before (see below).

A site building  benchmark run compared to `v0.31.1` shows that this should be slightly faster and use less memory:

```bash
▶ ./benchSite.sh "TOML,num_langs=.*,num_root_sections=5,num_pages=(500|1000),tags_per_page=5,shortcodes,render"

benchmark                                                                                                         old ns/op     new ns/op     delta
BenchmarkSiteBuilding/TOML,num_langs=1,num_root_sections=5,num_pages=500,tags_per_page=5,shortcodes,render-4      101785785     78067944      -23.30%
BenchmarkSiteBuilding/TOML,num_langs=1,num_root_sections=5,num_pages=1000,tags_per_page=5,shortcodes,render-4     185481057     149159919     -19.58%
BenchmarkSiteBuilding/TOML,num_langs=3,num_root_sections=5,num_pages=500,tags_per_page=5,shortcodes,render-4      103149918     85679409      -16.94%
BenchmarkSiteBuilding/TOML,num_langs=3,num_root_sections=5,num_pages=1000,tags_per_page=5,shortcodes,render-4     203515478     169208775     -16.86%

benchmark                                                                                                         old allocs     new allocs     delta
BenchmarkSiteBuilding/TOML,num_langs=1,num_root_sections=5,num_pages=500,tags_per_page=5,shortcodes,render-4      532464         391539         -26.47%
BenchmarkSiteBuilding/TOML,num_langs=1,num_root_sections=5,num_pages=1000,tags_per_page=5,shortcodes,render-4     1056549        772702         -26.87%
BenchmarkSiteBuilding/TOML,num_langs=3,num_root_sections=5,num_pages=500,tags_per_page=5,shortcodes,render-4      555974         406630         -26.86%
BenchmarkSiteBuilding/TOML,num_langs=3,num_root_sections=5,num_pages=1000,tags_per_page=5,shortcodes,render-4     1086545        789922         -27.30%

benchmark                                                                                                         old bytes     new bytes     delta
BenchmarkSiteBuilding/TOML,num_langs=1,num_root_sections=5,num_pages=500,tags_per_page=5,shortcodes,render-4      53243246      43598155      -18.12%
BenchmarkSiteBuilding/TOML,num_langs=1,num_root_sections=5,num_pages=1000,tags_per_page=5,shortcodes,render-4     105811617     86087116      -18.64%
BenchmarkSiteBuilding/TOML,num_langs=3,num_root_sections=5,num_pages=500,tags_per_page=5,shortcodes,render-4      54558852      44545097      -18.35%
BenchmarkSiteBuilding/TOML,num_langs=3,num_root_sections=5,num_pages=1000,tags_per_page=5,shortcodes,render-4     106903858     86978413      -18.64%
```

Fixes #3651
Closes #3158
Fixes #1014
Closes #2021
Fixes #1240
Updates #3757

1 files changed, 17 insertions, 3 deletions

diff --git a/i18n/translationProvider.go b/i18n/translationProvider.go
index e0eb89134..52aada8bd 100644
--- a/i18n/translationProvider.go
+++ b/i18n/translationProvider.go
@@ -17,6 +17,8 @@ import (
 	"errors"
 	"fmt"
 
+	"github.com/gohugoio/hugo/helpers"
+
 	"github.com/gohugoio/hugo/deps"
 	"github.com/gohugoio/hugo/source"
 	"github.com/nicksnyder/go-i18n/i18n/bundle"
@@ -73,9 +75,8 @@ func (tp *TranslationProvider) Update(d *deps.Deps) error {
 
 	for _, currentSource := range sources {
 		for _, r := range currentSource.Files() {
-			err := i18nBundle.ParseTranslationFileBytes(r.LogicalName(), r.Bytes())
-			if err != nil {
-				return fmt.Errorf("Failed to load translations in file %q: %s", r.LogicalName(), err)
+			if err := addTranslationFile(i18nBundle, r); err != nil {
+				return err
 			}
 		}
 	}
@@ -88,6 +89,19 @@ func (tp *TranslationProvider) Update(d *deps.Deps) error {
 
 }
 
+func addTranslationFile(bundle *bundle.Bundle, r source.ReadableFile) error {
+	f, err := r.Open()
+	if err != nil {
+		return fmt.Errorf("Failed to open translations file %q: %s", r.LogicalName(), err)
+	}
+	defer f.Close()
+	err = bundle.ParseTranslationFileBytes(r.LogicalName(), helpers.ReaderToBytes(f))
+	if err != nil {
+		return fmt.Errorf("Failed to load translations in file %q: %s", r.LogicalName(), err)
+	}
+	return nil
+}
+
 // Clone sets the language func for the new language.
 func (tp *TranslationProvider) Clone(d *deps.Deps) error {
 	d.Translate = tp.t.Func(d.Language.Lang)