Diff window improvements

[MaksymKapelianovych]

1. Returned back previous layout of graph panel (instead of SSplitter2x2). This allowed me to:

• reintroduce graph orientation changing
• add highlighting of all changed properties in details view (as well as highlighting focused one)
• add linked scroll bar to detail views

2. Fixed population of diff entries for tree, now hierarchy of add-ons are preserved in case if direct parent of add-on does not have any changes, but its grandparent has
3. Fixed focusing node in graph if user clicks on diff element, that belongs to add-on
4. Made detail views read-only