Allow browing by the intrument tree in the instrument window

[NickDraper]

Provide a tab showing a tree view of the instrument and allowing people to zoom to sections of the instrument by selecting from the tree.

The view should be placed in between the sample position and the selected item (could be a whole bank) such that the whole of the selected item takes up most of the screen.

Obviously you will have exceptions for this for the sample itself and the whole instrument.

[NickDraper]

This issue was originally trac ticket 292