Page Patching Part 1

Introduces an implementation of registry page patching in the spirit of what was available in Uru Live (Untìl Uru). This changeset bumps the prp version to 7 in some cases (currently, only for patch pages. pages pushed through the patcher are still version 6).

This is the first part of a series of work. Thus, this is only useful for internal experiments. Later changesets will improve the fileserver manifests and allow plResPatcher to apply patches on-the-fly.