Fix issue #108 : changes to clicking on filter - control-click to select/deselect filter, shift left/middle/right click to operate on first available output pin, control-shift click to operate on first available input pin.

git-svn-id: http://graph-studio-next.googlecode.com/svn/trunk@120 c2f33eb2-41b2-391d-4cb4-d9d0608729ba