Blender Git Loki

Made maya keymad deselect everything in cases nothing was selected with LMB

The way it works now is:

- Border select is using TWEAK, for which you need to hold LMB down
and move mouse. This prevents operators using RELEASE/CLICK events
from being fired.
- LMB select is using RELEASE event, this is no selection happens
before border if you do border select. And this prevents any
operator uses CLICK event from being fired.
- Delect all happens by CLICK, which would be fired only in case no
operators were handled with PRESS/RELEASE.

This is a bit cards-house, but this is how events currently works and
wouldn't want inventing something bigger now.