mplotqueries: toggle marker edges

Sometimes, in dense plots, the black circle edges can merge together to give
the visual appearance of a section of black (ie. the first group), which is not
actually the case.
mplotqueries: adjust marker sizes

Sometimes the dots are too big, and it would be nice to be able to adjust their
size interactively.
Merge branch 'markeredges' into mydevelop

Conflicts:
	mtools/mplotqueries/mplotqueries.py
Merge branch 'markersize' into mydevelop

Conflicts:
	mtools/mplotqueries/mplotqueries.py
mplotqueries: markersize: adjust help text slightly
Merge branch 'markersize' into mydevelop

Conflicts:
	mtools/mplotqueries/mplotqueries.py
Merge pull request #320 from devkev/mydevelop

marker sizes, marker edges, opacity.