Add more dances and syllabi

Thie patch implements additional syllabi - Quickstep, Foxtrot, Viennese Waltz and Tango. There is an additional two modules - syllabus, which represents which steps are considered part of the BDC syllabus for each of the dances, and routine, which provides a class to do common operations with sequences of steps, or routines. Additional tests have been implemented for all of these.