swpagerelsize ui: add new combo box for relative width relation

Change-Id: I0570fbfb5d36e476bb0a502509e9221c826ffa5c
swpagerelsize ui: read WidthPercentRelation from doc model

Change-Id: Idb5774bf2a51881b385433d3476bf27b5e9b0014
swpagerelsize ui: fix width percent value

Change-Id: I6f5b937826ac37f5f8bdee26e139fd6ca1e9a925
swpagerelsize ui: write WidthPercentRelation to doc model

Change-Id: Ia446566e7757f06c1bac12ae1d7a2392f20003a6
swpagerelsize ui: disable RelWidthRelation when RelWidthCB is not checked

Change-Id: I422f1f0d9b8436546ba355852fe6b3a21e2d1d23