Adding a drop down for the Milestones create/edit pages for selecting the milestone's group
Allowing user to choose milestone group within milestone create/edit pages, and displaying the group when viewing it.
Resolves Issue:99 and Issue:100.
Merge branch 'AssigningMilestoneGroupOnCreateEdit'
Fixing bug where pressing back button after pressing submit on the EditProgressIssue page would cause a NullPointerException.