Changed HashMap policy to be based on separate key and value policies.
Added a few type-specific flags bits to SlabThing alloc headers.
Added string object.
Removed 16-bit string objects.
Removed charAt and length from string.  Changed to bytes.
Added FNV hashing code.
Changed FNV hasher to be 32-bit only.
Fixed slab thing format so that header word always comes immediately before slabthing payload.
Started on rooting refactoring.
Added bitfield helper class.
Added HeapField helper container.