Changes to OS and browser SQL

- Use major version number in browser queries
- Remove mDot where clauses
- Add a combined OS and browser query
Browser support tables

First cut at a basic browser support table.

Waiting for https://github.com/guardian/frontend/pull/1269 before I can make this more useful.
Display a note that these are just mDot stats
Merge pull request #1270 from guardian/brower-support-tables

Brower support tables