Reformulate the way the kernel updates the PMAPs in the system when adding

Reformulate the way the kernel updates the PMAPs in the system when adding
a new page table page to expand kernel memory.  Keep track of the PMAPs in
their own list rather then scanning the process list to locate them.  This
allows PMAPs managed on behalf of virtual kernels to be properly updated.

VM spaces can now be allocated from scratch and may not have a parent
template to inherit certain fields from.  Make sure these fields are
properly cleared.