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
Then what about the case where we have glyphs and something else? Glyphs is an array, that something else might be a plain object. Now we have an array that looks like [[glyphs], object]. It's easier to flatten things out here than deal with nested arrays downstream.