Quick refactor on BucketsController
Add ApplicationService base class
Add PrioritizedIssueService class
Refactor PrioritizedIssuesController to use PrioritizedIssueService
Refactor BucketsController and BucketService

BucketService now inherits from ApplicationService and therefore has a
new API.
Merge pull request #59 from jonmagic/more-refactoring

More refactoring