Added GenerateLocale as SetMetadataSource predecessor, to avoid any
potential locale warnings. Also fixed a space indentation flaw and a
string which was being formatted with a non-existent key-argument.
This closes#75.
Three of the last developed plugins remained on the old `plugins/`
folder. This probably happened because they didn't existed when the
`documentation` branch were created, so they weren't moved when it was
rebased against `master`.
