more battle-proof purge action

Doesn't fail on timeouts so easily.
add jquery and jquery.makeCollapsible to be used in the future

jQuery 1.8.3.

jquery.makeCollapsible copied from mediawiki/core as of
commit 91e3622c9257427d37592ba630a939a3971c1e48.
adjust jquery.makeCollapsible to work without a MediaWiki around
make error messages collapsible