basic config for Content Security Policies

closes #7127

closes #7125

closes #7108

closes #7113

closes #7124

closes #7122

to have the license displayed in the projects header and inside GitHubs
License API

[ci skip]

closes #7121

Also fix a case where offline_since can be nil.

fixes #6220

closes #7120

closes #7119

closes #7089

closes #7066

Turns out that postgres can't handle "0" as boolean, but mysql can
handle "false".

closes #7115#pullrequestreview-699342

closes #7096

closes #7071

Also fixed the "fix public photos"-migration, because it didn't work
with migration-models :/

fixes #6177

Turns out there is a difference between hg and git and I should not
switch that often.

closes #7109

closes #7102

closes #7100

closes #7107

closes #7105

Signed-off-by: Lukas Matt <lukas@zauberstuhl.de>

closes #7095

closes #7094

fixes #7093