Modify StupidPool usage

* Change StupidPool to use a concurrent queue
* Modify OffheapBufferPool to pull from an expanding memory mapped file
This is a very dangerous change.

Previously, a `ResourceHolder` could only be either a `ResourceHolder` or a `Closeable` and would always represent the requirement that the object be closed.  By adding the `Supplier` interface, you are allowing this to be cast to a `Supplier` and then used from there, effectively losing the fact that it can and ***must*** be closed in order to be correctly used.

Please revert this.