Allow popovers to be attached to buttons.

These popovers will be activated once to guide the user to functionality
whenever the aloha toolbar plugin flashes the button.
Better styling for paste popover, more descriptive text.
Merge remote-tracking branch 'origin/master' into discoverable-copy-paste

Conflicts:
	templates/workspace/menu/toolbar-aloha.html
Reword the comment about what this does.
Merge branch 'discoverable-copy-paste' into testing