Revise BAIP-01: Purpose and Guidelines

Just my own opinion, the voting process (BAIP-threshold) should not be in the purpose and guidelines, but in a new BAIP, because it's a bit controversial. It's better to have a simple and relatively stable document as "purpose and guidelines".

I was listed as one of the editors, although I'd like to help when I have time, I don't always have time to respond quickly enough. It's better to have someone more suitable here, also good if we have guidelines about how to choose new editors.

Redefine the process. E.G. we're heavily relying on Github to collaborate, but not sending emails back and forth.

Start by reading BAIP-01 and the issue discussion, then identify which voting, editor-selection, and collaboration-process concerns belong in the purpose and guidelines. Done means the document has a stable scope, controversial voting rules are separated appropriately, editor guidance is addressed, and the revised collaboration process is agreed upon.

Written by the indexing model from the issue text.