Use custom form layout for Eclipse intro.

The current intro mechanism suffers from a number of issues
around html rendering. The URL links don't work on a bunch
of different platforms as per bug 41109.

https://code.google.com/p/android/issues/detail?id=41109

This CL uses SWT forms to render a simple page that provides:
 1. A button that opens the new project wizard.
 2. Links to documentation for first time users.

Change-Id: I9b5cf921b3cceb666e4e181e9e84109597731523