selectfeature via draggable box

patch requires #1070 for styling support

I agree this is needed.

I haven't thoroughly checked this out, but I'd like to before it goes in. The selection by intersecting bounds rubs me the wrong way. Point in poly and geometry intersection methods are not beyond what we can do here, and I'd like to give that a go before we commit to this. Also, I've always been annoyed by editing environments that ditch selected features when I'm trying to add new features to the selected bunch. Between shift, alt, and ctrl, we can have nice options for adding new features, removing from a selection, and selecting a fresh batch. I've implemented this elsewhere and it works nicely.

I think that having an 'intersectsBounds' (or just 'intersects') operator on the geometry would be nice, but I don't think it should be a blocker for putting this functionality in, if it's slow in coming. I'm willing to wait if you're willing to put the legwork in.

How do you envision the different actions working? I couldn't figure out a way to get the actual used key mask from the Handler.Box -- I had considered creating several Handler.Box handlers for different things, but thought that 'shift-dragbox' was magical enough, and that I didn't want to go more complex than that. The intersectsBox property on the control was a workaround.

removing review keyword pending further work on geometry.intersects() and inclusive vs. exclusive select handling.

I would like to give a second shot on this one. Any hints on what to start with ? Thanks.

Tests are OK (except MultiMap, and those recently broken See #1602)