Merge pull request #4904 from axilleas/master

Clear redis cache and precompile assets during update to 6.0. Fix #4874 #4840
Fix mailer tests
Set correct header border-bottom color for themes
Fix project_id field in MergeRequest API
Merge pull request #4916 from marbindrakon/merge_request_api

Fix project_id field in MergeRequest API
Improve user block logic

When block user - remove it from joined groups
Dont remove user from own resources (groups, users)
Merge branch 'master' of github.com:gitlabhq/gitlabhq