use git user in check script

No more separate gitlab user since 5.0.
Routing fix Commit-List: switch to branch with # in name
Commit List and Tree allow also + in branch name
replace font-awesome gem. Use fork icon
Error page if forking fails
IMprove stat-graph css
Solve inconsistency between network graph & stat graphs
use public_icon/private_icon helper
Merge pull request #4257 from jojosch/fix/routing-commit-with-#

Routing fix Commit-List: branch with # and + in name
Merge pull request #4244 from adaugherity/check_script_user

use git user in check script