Reflowed a few javadoc headers in DBEditObject

This just to try to reduce the amount of editor line-wrapping
that users might see when viewing / editing DBEditObject
Comments and @Override in gasharl userCustom

I copied a bunch of javadoc headers from DBEditObject that
have been elaborated since userCustom was created.

I added the @Override annotation to all methods that override
DBEditObject methods.

Tabs were also converted to spaces in this edit.
Added an EmptyVector class suitable for use as a singleton empty vector.
Reworked gasharl userCustom to use Java 5 generics, enhanced for loops.