Similar subtype

This PR introduces the possibility of filtering by subtype for the following elements:

* noteheads
* tremolo
* dynamics
* accidentals
I miss why you are using HEAD_HALF here. The filter text mentions the half note then but the filter is applied on notehead group only right?
Unfortunately we don't have yet a enumeration for these names but there is one hardcoded in inspector/inspector_note.ui Maybe you could extract it and use it here and in inspector?