Add a script to setup the transifex client config file.
Use `/usr/bin/env python` as opposed to `/usr/bin/python`.
Provide a script to update the source translation templates to Transifex.
Include script to compile the translation catalogs.
The translation template catalogs are under _build again.

Compile message catalogs for the desired language before generating the documentation.
Switch to anonymous links, simplifies translations.
Provide a script to simplify the translations download process.
Add information on how to build a localized version of the documentation.
Add a `download-translations` target to the `Makefile`.
Include the translating document in a `toctree`.
Update the translation doc to mention the `Makefile` target.
Merge pull request #7825 from s0undt3ch/features/i18n-documentation

i18n documentation updates