DOC: rename the shapes for randint distribution.

Make them match the numpy random_integer generator's.
DOC: rename the shape parameter for Von Mises distribution.

Now it matches the numpy one.
DOC: change the shape name for vonmises in stats tutorial
MAINT: remove LyX files from stats tutorial docs
Merge pull request #2921 from EvgeniBurovski/shapes

Stats: renaming shape parameters for several distributions