userportal,webadmin: show advanced options on validation error

When there was a validation error in the new/edit VM dialog while only the
basic mode was visible, it was not obvious what the problem is.

The new behavior is this:
- if there is a validation error and the invalid widget is visible in the
  current screen, do not show the advanced options
- if there is a validation error and the invalid widget is not visible, turn on
  the advanced options so the widget will be visible

To support this, the following changes had to be made:
- added the method isValid to HasValidation
- implemented this method in the needed widgets
- added the support of HasValidation also to the EntityModelWidgetWithInfo and
  DetachableWidget
- added a method getInvalidWidgets to DialogTab to find all the invalid widgets

Beside this also some small fixes has been done, namely:
- added the proper validation of the initial run tab
- fixed the validation of the system tab
- extracted and cleaned up the resetting of the tab validity

Change-Id: I1b419b560fe1e0bc0c8114d2a34f0bc930756aa0
Bug-Url: https://bugzilla.redhat.com/1085380
Signed-off-by: Tomas Jelinek <tjelinek@redhat.com>