Proposers guide improvements

[captainbrosset]

I went through the current proposers guide trying to put myself in the shoes of a person new to the project and found that its language could be improved in a few places.
So I'm proposing these improvements to the team:

• Simple language simplification.
• Addressed the reader as "you" instead of "the proposer", since this guide is for proposers.
• Changed "participants" to either "the Interop team" or "participating organizations on the Interop team" to avoid confusion where a newcomer would either not understand who is a participant, or even think they, themselves, are a participant.
• Clarified "use counter data".

[jgraham]

Thanks, but see the comment.