Update improved proposal Spreadsheet

Hey all,

I've updated an improved proposal for the spreadsheet.

For now I have completely restructured:


   - (re)Writing of Outcomes
   - Structure of Outcome based categorization
   - Proof Points for the Outcomes
   - Rewrote Proof Points (while keeping most)
   - Restructured spreadsheet based on comments in Github
   - Simplified spreadsheet (only for 3 dimensions now
   - Added a simple Rating / Scoring system added for evaluation of Maturity
   - Probably some more, see Github... :-)

All can be found at:

Jake's issues:
https://github.com/w3c/maturity-model/issues/created_by/jake-abma

Test Spreadsheet Simplified
https://docs.google.com/spreadsheets/d/1sbfh2Kone3Poe9CGw-llOriBPK3GnGDj3YY2GmDZH80/edit#gid=618390351

Much more to come soon!

Cheers,
Jake