Fix #34350: Maya Keyboard map preset problems

Two main things:

- Made a python operator for selection in a viewport
  which will de-select everything if nothing is under
  the mouse.

  To do so needed to modify VIEW3D_OT_select, so invoke
  sets mouse location which is later used by exec
  function.

  This way it's possible to select stuff from python
  defined operator.

  Not best-ever solution since ideally exec() shall not
  do OpenGL stuff, but we've got this issue in some
  other operators. We'll solve this later.

- Used a keymap from Gianmichele Mariani as a reference,
  updated his keymap to latest changes in operators.

  We shall match Maya keymap much better now, thanks
  for the keymap dude!

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@56209 954f8c5b-7b00-dc11-b283-0030488c597c