Added Hair Child Support 
note: rendersteps seem closer to BI with power of 3 rather than 2 as said in the UI Py tooltip.

git-svn-id: https://svn.blender.org/svnroot/bf-extensions/trunk/py/scripts/addons@4246 96b784f8-4ae3-dd11-aff7-0030488c597c
fixed vertex weight handling of more than 3 bone weights, that milkshape cannot support.

indirect part of the reported issue:
http://www.blender.org/forum/viewtopic.php?t=26251

now, vertex weights will sorted according the weight. in case of more than 3 weights, less important ones will be skipped on export.

git-svn-id: https://svn.blender.org/svnroot/bf-extensions/trunk/py/scripts/addons@4248 96b784f8-4ae3-dd11-aff7-0030488c597c