frontend: introduce generics to UICommon (part 3)

Infrastructure part of the introduction of the generics into UICommon

Changes:
- created the generic versions of the following widgets:
  EntityModelCheckBox(Only), EntityModelRadioButton, EntityModelTextBoxOnly
- Deleted the EntityModelSliderWithTextBoxEditor and EntityModelInputWithSlider
  since not used

Change-Id: I39c221076b706d77c7c1facfbd5d668a2082df72
Signed-off-by: Tomas Jelinek <tjelinek@redhat.com>