IDE-1107

Add a liferay-display.xml category name validator to show warning when user types empty category name only the name only contains spaces in the category element property.
Use proper IvyDE API
IDE-1128

    Changed the validate() method into compute() which fix the latest builded
    sapphire breaking the liferay IDE build problem.
IDE-1122

Let the progress monitor display message about ivy downloading and
resolving artifacts(particularly the first time the plugins-sdk is used it
can take sevaral minutes), in case users mistakenly think the IDE is
blocked.

Signed-off-by: Gregory Amerson <gregory.amerson@liferay.com>