Glyph actions

Covers https://github.com/KSHSK/WAVED/issues/227, https://github.com/KSHSK/WAVED/issues/206, https://github.com/KSHSK/WAVED/issues/286, https://github.com/KSHSK/WAVED/issues/295

Edit: Incidentally also covers https://github.com/KSHSK/WAVED/issues/269
I assume this is for future changes if/when glyphs can be event triggers?