Don't allow pre-1.0 to upgrade past 1.0. #1521

For the 1.0 release, the response from:

http://api.piwik.org/1.0/getLatestVersion

should be frozen as 1.0.

The url in core/UpdateCheck.php should change to:

http://api.piwik.org/2.0/getLatestVersion

This will allow us to:

• clean up some of the code (e.g., remove any deprecated methods, obsolete core/Updates/* files)
• add expected file length (of latest.zip) and sha1 hash to response (compat buster)
• reduce end-user support for users upgrading from 0.x to 1.x, i.e., we can focus on 1.0 to 1.x

sounds like a good idea,
but I vote to do this in 1.x first release (it doesn't matter when we do this I think?)

1.0 is an arbitrary cut-off. Whatever version we do this becomes the cut-off as it requires a change in core/UpdateCheck.php and on the server.