Upload an alternative draft version of a pmOS vendor agreement

Here are some thoughts from me as to an agreement with vendors. Please treat it as a strawman, for discussion. I have tried to take into account as many of the points from the current discussion as I can.

FOR THE TEAM: Please let's discuss the core points in https://notes.postmarketos.org/docs/ef256d02-cfd7-440a-bb86-016b3cffc17c/ and only after that is approved talk about the legal part.