Create vertex-buffer driven object for stamping music symbols

[MarkOates]

This is just a note dump:

- custom vertex

- glyph
  - custom vertex
    - color
    - vertex has id

- stamps
  - id
  - multimesh_id

- vector<stamp> stamps

- add_stamp()
  - x, y, thing_to_stamp
  - add stamp to stamps
  - create multimesh entry
  - assign multimesh_id to stamp

- remove
  - remove from multimesh
  - get result_id
  - find stamp with multimesh_id
  - reassign multimesh_id to result_id