Update build tool to download proj4.js from github
Update externs for new proj4.js API
Change proj functions to use the new proj4.js API
Update tests

The GML snippets use 'foo' and 'FOO' as srsName. The old proj4js
silently failed on such unknown srs names, but the new proj4.js
throws an exception. There is also no magic to lowercase compare
proj codes any more, so we need to define srs codes properly.
Update examples