Add an 'unit-change' event fired when shift+click on color and angle swatches.
Add a listener on this event in text-property-editor.js to call the same function
that's called when tooltip edit is commited to persist the new unit.
Edit some tests to adapt to this new behaviour and create some tests to make sure
the value obtained via shift+click are actually persisted.
MozReview-Commit-ID: CcF4oiBPEzT
--HG--
extra : transplant_source : %1B%40%A24%EDW.%C5%96%C8m%3C%1F4%DA%F78%D1%26%8B
Add a swatch before angle values in the rules panel and allow cycling
through angle units with shift+click (like we already do for color units).
MozReview-Commit-ID: CWhoUQTkP1G
--HG--
extra : transplant_source : %5B%E5%AD%22%D2%20uk%07%EE%A9%E4%91YS%B3R%C3%DF%21
