If welcome is enabled, use it to recover from a forgotten password (Closes hhucn/adhocracy.hhu_theme#243)
Improve password reset message when welcome_back is enabled
Remove useless files.

To my surprise, adhocracy works perfectly fine without these files. The only reference I can find is to plain.css
Merge branch 'develop' into welcome_back

Conflicts:
	src/adhocracy/lib/message.py
Merge remote-tracking branch 'liqd/develop' into welcome_back

Conflicts:
	src/adhocracy/controllers/user.py
	src/adhocracy/lib/auth/welcome.py
Fix syntax error
[welcome] Do not require password to be unset, and support the case of both welcome_code and reset_code
i18n "Forgot your password?"
Merge pull request #336 from phihag/welcome_back

Welcome back users who forgot their passwords
typo
Merge pull request #338 from phihag/remove-useless-files

Remove useless files
Restored missing icon

The user icon has been removed in
9d69341247a81523ce3019ffcd33095cb2c1d86e, although functionality is
still in used.
Merge remote branch 'origin/develop' into alternative-login-form

Conflicts:
	src/adhocracy/controllers/user.py