Removed code dealing with models
removed node_info structure and got rid of distance cacheing
SVS - version that compiles after removing node_info and models
SVS - new version of filter base class and typed_filter implemented and compiles
SVS - new version of filter base types implemented and compiles
SVS - removed scene_sig from code
SVS - separated algorithms for nodes into separate sgnode_algs files
SVS - refactored and tested absval_filter class
SVS - First pass at bbox filter
SVS - made an explicit template specification for typed_filter<sgnode*>
SVS - more tweaks to how typed_filter<sgnode> works and added node filters
SVS - removed all filters for refactoring and changed sgnode algorithms
SVS - changed node properties to tags and added new commands
SVS - added base filter types for node filters
SVS - added distance filters
SVS - added volume filters
SVS - added distance_on_axis filters
SVS - added intersect and contain filters
SVS - add tag_select filter
SVS - lots of filter bug fixes and cleaned up commands