Milky/feature bandbox

[milkmanmatty]

Builds upon #12 gui state

Main Functionality

Add ability to bandbox select features. The new feature bandbox selection should be free-form and not snap to the grid.

Notable Side Effects

This PR adds a static reference to a FeatureService to the FeatureInstance class. It seems baffling that a FeatureInstance cannot tell what feature it is. There may be a good reason for the ommision, it seems that TA features may only have a name to identify themselves and this is a carry over from the domain that Mappy models (possibly not though?).

Bugfix

An attempt was made to fix/workaround the BatchMoveFeatureOperation bug. The bug assumes that the destination of any feature does not contain another feature that is also about to be moved.

Functional Requirements:

• Bandbox selection is free-form mode when the Features gui tab is active.
• Bandbox selection is the tile-based default when any other tab is active.
• Free-form bandbox selection does not snap to the grid.
• Features contained within the free-form bandbox selection are selected upon mouse button release.
• Features are considered within the bandbox when the feature's image midpoint (both X & Y) is within the bounds of the bandbox.