Fix issue with FieldtypeDatetime keeping rows for empty values per @teppokoivula issue #284
Fix for @felixwahner issue #279 (uninitialized vars in PageRender::getCacheFile)
Attempt fix for CacheFile not getting deleted issue as reported by Pete.
Addition of some utility/convenience functions in the core, mostly applicable to WireArray. See the commit in file WireArray.php for detailed comments on the new additions.
Some additional tweaks to the WireArray API additions.