PreparePKM had the opportunity to be recursive (preparation ->
validating*N -> preparation*N), lock out preview sprite updating (which
calls PreparePKM via Main.cs) while validating all controls
remove uncallable paths (format is checked prior, and checksum check is
never called as fieldsInitialized is forced false)
move gui toggling to loading methods when appropriate
extract pkm loading routines to smaller methods
reduce code duplication (rely on empty setters to ignore some calls)
should be much easier to understand the load/save process; the original
setup (pk6) was following the structure from 0x00-end, no point still
doing that as everything is now abstracted.
