Don't include StudioInfo synths in help system:

* These are internal synths synths such as the mixer and the sample player
Rename all synths to have a sonic-pi- prefix to remove chance of clashing with external synths. Also:

* add new synths:
  - pulse
  - pulse_s
  - tri
  - tri_s
  - saw
  - saw_s
  - mod_fm

Note, saw_beep is now just saw. 

Also separate synth name from name users use to trigger synths - allows names to be changed without having to recompile synths.
Prefix all examples with one of:

* apprentice
* illusionist
* magician
* sorcerer
* wizard

To help denote complexity. Order is from apprentice to wizard (also happens to be alphabetical ;-)