WIP... mostly working two tests failing...
WIP... moved isscalar to Axis... but I feel it is not the right way to go.
Merge branch 'master' into novgticks

Conflicts:
	larray.py
change isscalar tests to contains, as it is really what we need to test
cleanup and comments
add a few tests (notably for named groups) and fixed some tests (mostly the contains tests I just introduced)
all tests pass! After all keeping ValueGroup ticks does not make things more complicated, so I added them back in!
    * to_label adds a ',' at the end of lists of one elements
    * accept python3 range objects as an Axis ticks
    * fixed targeting a VG tick by its name