rework start
tweak some comments
add elements more intelligently
remove items recursively
make lightgroup more consistent in terms of trigger_intensity
mess around with spawning
twiddle effects trigger from group trigger
move trigger_intesity set
disable trigger_intensity set
a start at docstring based ref docs

still need to decide whether to style with autodoc
or numpydoc or ...
Merge branch 'master' into spawn-improvements

Conflicts:
	birdfish/lights.py
add step method to lightshow

very useful for debugging
added universal update_active property for nested elements
pep8 and label dispatch keys for chase example
finish update_active and spawn fixes

including a provision to only update an element
once per show update, even if it is used in several
elements