A variety of operators were missing appropriate bl_options for correct
undo support.
This results in either crashes (auto loft, bi-rail) or other odd
behaviors around returning the scene to the correct previous state
(sometimes having to hit ctrl-z twice to undo once, sometimes undo skips
steps, etc.)
Differential Revision: https://developer.blender.org/D13283
Reduces warnings while running tests.
Also fix some descriptions with strings concatenated but without a
space in between.
Reviewed by campbellbarton
Differential Revision: https://developer.blender.org/D9655
