Summary of changes:
- kernel/mem renamed to kernel/mm
- consolidated page/frame defs into one file which now lives in the
kernel/mm package and is referenced by both pmm and vmm pkgs
- consolidated parts of the vmm code (e.g. PDT+PTE)
- memcopy/memset helpers moved to the kernel package
- physical allocators moved to the kernel/mm/pmm package
- break vmm -> pmm pkg dependency by moving AllocFrame() into the mm
package.
