Created Tree Branch
Includes Tree Model and Node Classes
Copied Controller and RequestObserver from ListView to retrieve Requirements from the database
Fixed nullPointerException
Tree will now load in requirements when it is focused (on start up)
Refresh Button loads in requirements (will make it auto-refresh later)

Bug: Refresh button will re-add requirements that are already in the list
Cleaned up code, and deleted unused files.
Fixed bug with refreshing the tree, no more duplicate nodes
Cleaned code
Cleaned Code
Default view is now expanded
Iteration node is just a place holder
Merge remote-tracking branch 'origin/team1-tree' into team1-table