Skip init script checks on omnibus-gitlab

Omnibus-gitlab does not use the init script.
Load last commit for files per 10 items.

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Merge branch 'files-rational-git-log' into 'master'

Split commit logs loading

#### Before this MR

When visit files tab we have ajax call that loads all last commits for files inside directory.
Load time depends on amount of files in directory. So if directory has 100 files - you may need to wait up to 20 seconds to get last commits info of files. Still if you do navigation at this time the request still wait for processing taking workers busy. If several people try to navigate through big repository directories - you will see huge performance drop.

#### After this MR

Load last commits only for first 10 entries. It usually takes not more then a second (even for huge repos). If user still on the same page - do next ajax call and get 10 more entries. If user navigate to another directory - stop ajax calls for this directory. So for cases when you want navigate to nested directory - you don't have long-running ajax calls that takes workers and makes app unusable for other users

- - -

Fixes #1229
Merge branch 'detect_omnibus' into 'master'

Detect omnibus-gitlab in `rake gitlab:check`