added description field to filter record
basic filter tree structure
added filter box and basic record filter UI (not functional yet; only supporting on-the-fly filters for now)
repalced std::auto_ptr with boost::shared_ptr in filter nodes
replaced binary filter node with a n-ary node
added parser and custom filter edit widget (parser not functional yet; always returns a false boolean node)
fixed BooleanNode constructor
apply filter to table after filter text change
automatically build column map on filter change
added error reporting in the filter edit widget (change the text colour for now)
some general filter parser cleanup
simplified filter system by taking out filter references and user values for now (these are post-1.0 features anyway)
added and and or filter nodes
added not filter node
fixed an include guard
added text filter node
made text node filter case-insensitive
fixed string parsing