We already do it for variables and functions, so that any new feature
won't need the ace files to be edited. I originally didn't implement it
for keywords too, but it's actually much better this way.
Change-Id: I1ee81feace2ea90d5dbb2e443f01bc0f6cf74eb7
Replace the conditions textarea with Ace editor for editing and testing
filter. This uses a soft dependency on CodeEditor; if the latter isn't
installed, the classic textarea is used. The user is still able to
switch between the editors on the go; the new buttons may look a bit
ugly now, but after switching to OOUI they should get much better.
Finally, added a custom syntax highlight for AbuseFilter rules.
Bug: T39192
Change-Id: If3d6a994142e34686bb7fc9f09093f751b599485
