Changes based on review comments
Fix merge error (WORKING_SET_VIEW) and update working set test.

The DOM structure has changed a little in the tree.
Fix problem with DragAndDrop test.

This was very hard to track down because our promises and event handlers swallowed
an exception thrown in FileTreeViewModel.
Fix problem with InlineEditorProviders-test.

The project files cache was not being cleared on every file system change, as it had
been previously. Also removed duplicate projectClose event.
Fix context menu behavior when you right click from one node to another.
Merge branch 'ProjectManager' of https://github.com/adobe/brackets into ProjectManager
Revert "- fixed typo in FileViewController.WORKINGSET_VIEW which caused errors opening files from working set"

This reverts commit 83b95c402b5ccfa1ac679bf05908545e86d742ca.
Another couple of WORKINGSET_VIEW cleanups