(bug 22209, bug 22574) Make indent, bullet list and numbered list buttons in the...

(bug 22209, bug 22574) Make indent, bullet list and numbered list buttons in the WikiEditor toolbar act on each line individually

* Reintroduce support for the splitlines argument in encapsulateSelection(). Was implemented by Adam Miller in r61493 but got lost somehow
* Add 'splitlines': true for the bullet list and numbered list buttons. The indent button already had it, so that part of r61493 did survive
* Copy options.pre and options.post to local pre and post variables instead of using (and modifying!) them directly all over the place