Enhancement : Lazy loading of editor pages

Editor pages should only be loaded when the user switches to the page.

Bugzilla: https://bugs.eclipse.org/bugs/show_bug.cgi?id=444202
Signed-off-by: Gregory Amerson <gregory.amerson@liferay.com>
Enhancement : Lazy loading of editor pages

Re-worked the API to minimize the amount of code required when extending
from SapphirEditor and to ensure full backwards compatibility.

Bugzilla: https://bugs.eclipse.org/bugs/show_bug.cgi?id=444202