Rename ObjectPool to HandleTable
Kernel: Replace GetStaticHandleType by HANDLE_TYPE constants
Kernel: New handle manager

This handle manager more closely mirrors the behaviour of the CTR-OS
one. In addition object ref-counts and support for DuplicateHandle have
been added.

Note that support for DuplicateHandle is still experimental, since parts
of the kernel still use Handles internally, which will likely cause
troubles if two different handles to the same object are used to e.g.
wait on a synchronization primitive.
Merge pull request #331 from yuriks/handle-reform

New Handle manager