webadmin,userportal: Add workaround-related info in UI code

This patch adds information on notable workarounds related to
3rd party code (GWT, GWT-Platform) by means of Java comments
in following format:

  // TODO-GWT: description goes here

When upgrading versions of 3rd party dependencies, comments
on notable workarounds will make it easier to review existing
UI code during the version upgrade.

Change-Id: I336da10b2931825a7b44c24b663e18593f489979
Signed-off-by: Vojtech Szocs <vszocs@redhat.com>