Implement the main flow for the Exporting Engine (#7149)

* Add top level tests

* Add a skeleton for preparing buffers

* Initialize graphite instance

* Prepare buffers for all instances

* Add Grafite collected value formatter

* Add support for exporting.conf read and parsing

* - Use new exporting_config instead of netdata_config

* Implement Grafite worker

* Disable exporting engine compilation if libuv is not available

* Add mutex locks

- Configure connectors as connector_<type> in sections of exporting.conf

- Change exporting_select_type to check for connector_ fields

* - Override exporting_config structure if there no exporting.conf so that
  look ups don't fail and we maintain backwards compatibility

* Separate fixtures in unit tests

* Test exporting_discard_responce

* Test response receiving

* Test buffer sending

* Test simple connector worker

- Instance section has the format connector:instance_name
  e.g graphite:my_graphite_instance

- Connectors with : in their name e.g graphite:plaintext are reserved
  So graphite:plaintext is not accepted because it would activate an
  instance with name "plaintext"
  It should be graphite:plaintext:instance_name

* - Enable the add_connector_instance to cleanup the internal structure
  by passing NULL,not NULL arguments

* Implement configurable update interval

- Add additional check to verify instance uniqueness across connectors

* Add host and chart filters

* Add the value calculation over a database series

* Add the calculated over stored data graphite connector

* Add tests for graphite connector

* Add JSON connector

* Add tests for JSON formatting functions

* Add OpenTSDB connector

* Add tests for the OpenTSDB connector

* Add temporaty notes to the documentation

2 files changed, 4 insertions, 1 deletions

diff --git a/daemon/common.h b/daemon/common.h
index df36a49d4e..c04c8ad04f 100644
--- a/daemon/common.h
+++ b/daemon/common.h
@@ -27,7 +27,6 @@
 
 #define config_generate(buffer, only_changed) appconfig_generate(&netdata_config, buffer, only_changed)
 
-
 // ----------------------------------------------------------------------------
 // netdata include files
 
diff --git a/daemon/main.c b/daemon/main.c
index ee2a437fd0..f8c6d84d45 100644
--- a/daemon/main.c
+++ b/daemon/main.c
@@ -75,6 +75,9 @@ struct netdata_static_thread static_threads[] = {
 
         // common plugins for all systems
     {"BACKENDS",             NULL,                    NULL,         1, NULL, NULL, backends_main},
+#ifdef ENABLE_EXPORTING
+    {"EXPORTING",            NULL,                    NULL,         1, NULL, NULL, exporting_main},
+#endif
     {"WEB_SERVER[static1]",  NULL,                    NULL,         0, NULL, NULL, socket_listen_main_static_threaded},
     {"STREAM",               NULL,                    NULL,         0, NULL, NULL, rrdpush_sender_thread},
 
@@ -1105,6 +1108,7 @@ int main(int argc, char **argv) {
     if(!config_loaded)
         load_netdata_conf(NULL, 0);
 
+
     // ------------------------------------------------------------------------
     // initialize netdata
     {