Parts of the tool icons for box, circle, lasso, and tweak select that were
meant to be flat or at a 45 degree angle were slightly misaligned, making
the edge look blurry.
- Tweaked icons for Box Select, Circle Select & Lasso Select.
- Tweaked icons for Rip Region & Rip Edge.
- Added icons for Bone Envelope, Bone Size, Pose Breakdown,
Pose Push & Pose Relax.
- Added icons for curve Extrude, Extrude Cursor.
Also removed grease pencil mirror tool which wasn't an active tool,
and is now consistent with regular Edit Mode.
