Floating Palettes: Create the ActionMode type and use it in Editor.

This CL creates the Type attribute for ActionMode, which will serve as a flag to determine its behavior and representation.
- TYPE_PRIMARY is the default and will maintain the current behavior and representation in the ActionBar
- TYPE_FLOATING will be the new Type and will be represented as a Floating Palette

Editor switches the flag from the default to TYPE_FLOATING, but this has no consequences right now, until the functionality is implemented.

Change-Id: Icd6cab01637f6ca3ae2e999b06904e08974d0c81