Replace failure with anyhow in complete codebase

This patch was scripted with

    sed -i 's/use failure::Error/use anyhow::Error/' $(rg "use failure::Error" -l)
    sed -i 's/use failure::Fallible as /use anyhow::/' $(rg "use failure::Fallible" -l)
    sed -i 's/failure/anyhow/' $(rg "failure *=" -l)
    sed -i 's/format_err!/anyhow!/' $(rg "format_err!" -l)
    sed -i 's/use failure::ResultExt/use anyhow::Context/' $(rg "use failure::ResultExt" -l)
    sed -i 's/err_msg/anyhow!/' $(rg "use failure::err_msg" -l)
    sed -i 's/^anyhow\ *=.*$/anyhow = "1"/' $(rg "anyhow * =" -l)
    sed -i 's/^anyhow_derive.*//' $(rg "anyhow_derive" -l)
    sed -i 's/extern crate failure/extern crate anyhow/' $(rg "extern crate failure" -l)
    sed -i 's/.*extern crate anyhow_derive.*//' $(rg "anyhow_derive" -l)

Some manual changes were added as well, so this patch was not completely
scripted, but mostly.

Signed-off-by: Matthias Beyer <mail@beyermatthias.de>