[IMP] *: Generate .pot files and push them to GitHub

[luisg123v]

This bring changes made in https://github.com/OCA/maintainer-quality-tools/pull/556

The following eleven commits are included:

• add travis_makepot
• run makepot if TRANSIFEX=1
• remove transifex support
• remove weblate support
• update sample .travis.yml
• Run makepot only on OCA repos: We don't wan't it to run contributor branches if they have enabled travis.
• remove unused code
• configure git user name and email before commit
• run makepot on 8.0, 9.0, 10.0, 11.0 branches only
• add copyright/license header
• run msgmerge only if a new pot file is created: After that, weblate will run msgmerge itself each time a pot file is updated. This is to make sure the vast majority of .po files change occur on weblate side, to minimise git merge conflicts.

Original author is referenced in the commit message.

This is the first step to solve https://github.com/Vauxoo/maintainer-quality-tools/issues/265

[luisg123v]

@moylop260 This is ready for review