core: Fix syntax errors on postgres
Pick 2.5.1.1 release notes
Fake staticpages initial migration only for 2.5.0

staticpages was added as legalpages in 2.5.0, so for older releases it
is necessary to run all the staticpages migrations, but for 2.5.0 the
initial migration needs to be faked.

This allows to directly upgrade without problems from releases older than
2.5.0.
Make setup command code sligthly more readable
Docs: Record upgrade fix in release notes
Docs: Update detailed upgrade instructions
Minor cleanups
Cleanup: Remove unnecessary CSS styles