Large refactor to Formula, mostly improving reliability and error handling but
also layout and readability.
General improvements so testing can be more complete.
Patches are automatically downloaded and applied for Formula that return a
list of urls from Formula::patches.
Split out the brew command logic to facilitate testing.
Facility from Adam Vandenberg to allow selective cleaning of files, added
because Python doesn't work when stripped.
Because cmake syntax is batshit-insane, this stops people having to memorize
which parameters to supply, and thus prevents error.
I didn't do the same for Autotools deliberately as I have found that
which parameters are supported is somewhat inconsistent. Plenty don't even
support --disable-debug, thus I want the parameters getting used in the
contributors face so they can easily diagnose what is going on.
