Trigger events when moving, creating or deleting files/directories

[Alhadis]

There's currently no reliable way to detect when a user's renamed or moved a file in the tree-view. Filesystem events such as did-destroy are by no means fit for detecting a file's deletion; such events are also triggered on File objects when dragging FileView objects between folders.

Furthermore, it's difficult to determine a file or directory's previous path when responding to a path change. Short of individually monitoring every file and directory's status, package authors have no easy way to respond to user-directed changes in the filesystem.

This PR addresses this matter by introducing a number of events that're emitted at certain points in the tree-view's lifecycle:

• directory-created
  • path: Resolved/normalised path of the directory
• entry-copied
  • oldPath: Path to source file/directory
  • newPath: Path of newly-created file/directory
• entry-deleted
  • path: Last-known path of a deleted resource
• entry-moved: Self-explanatory. Invoked by both cut-and-paste as well as drag-and-drop/rename.
  • oldPath
  • newPath
• file-created
  • path: Resolved/normalised path of the file

These events are emitted on the main tree-view instance, which is accessible through both the DOM as well as via atom.packages.activePackages["tree-view"].mainModule.treeView.

[Alhadis]

Bloody hell, I do write some crap, don't I.