Changement de la documentation de SFLVault : RT 213228
client: Add support for python-keyring > 2.0
Improve comments to better explain double authentication

ref #46143 and #9440
Brought back sfl-sflakes checks

There were tons of pep8 violations, way too many for immediate fixes, so
there's a big list of ignores for now.
Ignore build folders in sflakes checks
Fixed copyright-related sflakes errors
Moved sflvault.common into SFLvault-client package

This removes the need for a SFLvault-common package.
Prepared client v0.8 release changelog

v0.7.9 was never released so I've just appended to the changelog.
Merge branch 'develop' into build-refactor

Conflicts:
	client-qt/setup.py
	client-qt/sflvault/clientqt/gui/config/preferences.py
	client/setup.py
	common/setup.py
	server/setup.py
Removed dangling references to sflvault-common