frontend: ListModelTypeAheadListBox adjustements

This patch contains the following changes:

1: changed the styling of the suggestions to make the size
   proportional to the content
2: changed the styling (added bottom borders and changed the coloring)
3: the selected item is now the one set as setValue()

Change-Id: I4ff487d93b752540feb7b9e9392fae1479662d59
Bug-Url: https://bugzilla.redhat.com/997422
Signed-off-by: Tomas Jelinek <tjelinek@redhat.com>