70513102 Performance for some pages

- fixed N+1 query issues in comments and tasks renderings
- fixed some N+1 issues in status bar for (ContentPlan details page and Dashboard page)
- added caching for comments and tasks
- corrected related Rspecs, related to ContentPlan status bar
Merge pull request #64 from bitzesty/70513102-performance-for-detail-pages

70513102 Performance for some pages