#4750: Added going to object on dblclk in graph

- Uses signal/slots: graphView signals that we need to go to object,
other views catch it and use object to look how to go to it.
- Some code duplication, although seems reasonable.
- Added a couple of fields to easy-access to data.
- No data-changing on-air checking.
Merge branch 'devel' into #4748-9