Add support for auto-completing placeables
Improve placeables inside right-to-left text

Make them embedded left-to-right strings so that things like “%(foo)s”
do not look like “foo)s)%” inside right-to-left strings (which can be
seen when setting, say, Arabic as an alt source language).

This does not affect translation field (which would benefit from this
most), though.
Fix the placement of the auto complete drop down

For some reason we need to force block here otherwise the placement is
off in Firefox.
Escape HTML in autocomplete dropdown