[Enh] Adding functionality to TestHelpers.
[Fix] Fixed some tests that were running OK by themselves, but were failing when run in the context of the whole suite.
[Enh] PluginTranslationOf: When saving a page that contains this kind of plugin, a tiki.wiki.translationof relation is created between that page and the future translation of the link.

git-svn-id: file:///var/local/code.tiki.org/tikisvn/trunk@47937 b456876b-0849-0410-b77d-98878d47e9d5