New header METAs proposal

[Orion Pobursky]

But I'm wondering if this should be in the part files them selves. It might be easier to maintain in a LDConfig.ldr like additional file.

In Part file
Pro: The external number is searchable.
Con: The part file itself is edited if there are changes.

Separate file:
Pro: Significantly easier to maintain.
Con: Searching is more complicated.