simplify mapper directory layout
remove old unused have_new_mapper_state cruft
shorten/simplify screen range names
decouple axis and grids
remove need for location parameter to axes
merge master
adjust mpl.py to use new changes
some test fixups
Merge branch 'master' into feature/gridaxes
remove old parameter from test
communicate mapper type
improve readability
Merge pull request #996 from ContinuumIO/feature/gridaxes

grid and axes improvements