Implement Stack (menu) Tool

There are two stacks tools
- A Stacks Menu tool which when clicked pops up a menu of stack related commands that can be activated
- A Stack Tools command that when activated fills the tool bar with a few stack oriented tools like start/stop animation (>), first slice (<<), last slice (>>), next slice (>), prev slice (<), add data (+), and delete data (-).

Migrated-From: http://trac.imagej.net/ticket/951

No files, tests, or entry points are named. Start by inspecting existing ImageJ tool plugins and how menus and toolbars are registered. Done means a Stack Menu opens stack-related commands and Stack Tools provides the listed animation, slice navigation, add-data, and delete-data actions.

Written by the indexing model from the issue text.