* unified some class/method/member names
* unified change notifications: removed the observer pattern in
favor of signals/slots connections
* shared_ptr is now used for memory management of aspects, columns, and filters
* column commands now operate on ColumnPrivate only (following the model
that the commands are really between Column and ColumnPrivate)
* all abstract classes use a wrapper for signals and slots, this
avoids the need to have QObject as a base class and prevents
multiple inheritance problems
* test status: aspect-test runs and column-test is passed w/o error
* known issues: some doxygen comments need to be updated to
the current implementation; some aspect related methods
are not yet properly implemented in the filter classes
