added contains/containsnot conditional

It seems not to be possible to write own conditonal modifiers as snippet, so I would like to add them to the core.
Added method for clearing cache of resource

I think it is vary useful method, that is need for many developers.
I use it in my component and can do just
<pre>$res = $modx->getObject('modResource', 15);
$res->clearCache();
</pre>
Fix same categories on other parent levels. See tracker issue #9052
Add modResource::clearCache() to remove cache for single Resource

Merge remote-tracking branch 'origin/pr/428' into pr/428

* origin/pr/428:
  Added method for clearing cache of resource
Fix cache provider options in modResource::clearCache()
sigh, fixing commit message
Add case-insensitive contains/containsnot conditional output filters

Merge remote-tracking branch 'origin/pr/406' into develop

* origin/pr/406:
  added contains/containsnot conditional
Allow Categories to have same name with different parents

closes #432

Merge remote-tracking branch 'origin/pr/432' into develop

* origin/pr/432:
  Fix same categories on other parent levels. See tracker issue #9052