Added new features to plugin and Topcoat Effeckts

- Added ability to delete files/folders and create new folders in the
Dropbox plugin.
- Updated sample app UI with Topcoat Effeckts.  Added Topcoat overlay
and off screen nav menu with Effeckt CSS that uses webkit animations and
transforms.
- Added a fix to the viewport in the sample app for Android 4.4 and
higher.