* Implementation for calculating language statistics
Impement saving code language statistics to database
Implement rendering langauge stats
Add primary laguage to show in repository list
Implement repository stats indexer queue
Add indexer test
Refactor to use queue module
* Do not timeout for queues
* Change graceful to use a singleton obtained through GetManager instead of a global.
* Graceful: Make TestPullRequests shutdownable
* Graceful: Make the cron tasks graceful
* Graceful: AddTestPullRequest run in graceful ctx
* Graceful: SyncMirrors shutdown
* Graceful: SetDefaultContext for Xorm to be HammerContext
* Avoid starting graceful for migrate commands and checkout
* Graceful: DeliverHooks now can be shutdown
* Fix multiple syncing errors in modules/sync/UniqueQueue & Make UniqueQueue closable
* Begin the process of making the repo indexer shutdown gracefully
