Fix EZP-23459: eZContentObjectTreeNodeOperations::move missing features

Ensure that it checks whether view caching is enabled before clearing it.
Ensure that CacheThreshold is respected, if exceeded clear all cache.

https://jira.ez.no/browse/EZP-23459

(Part 3: Defer to script monitor will be moved to a separate issue)
1. OK (seems that whenever I copy code from elsewhere in the kernel, I get such responses... :)
2. Gah. Where is this CS specified? Didn't see anything like it here: https://github.com/ezsystems/ezpublish-kernel/wiki/codingstandards