Add an abstract base class to make deleting objects easier.

Similar to AdminObjectEdit, but not quite as polished for now.

Looking forward to suggestions to improve it, but it currently supports loading and deleting dataobjects and record sets fairly easily, which brings with it memcache clearing, and code reuse.

~~The confirmation message is still left to the developer to build.~~

There is now confirmation message support, which is left to the developer to use, or ignore.