Add javascript for Object Code excanvas (flot) version herein included and use that instead of minified version.

I had a bit of trouble finding the upstream on excanvas, as the version from
Google, which appears to be the original source, seems unmaintained.

However, it appears the version we're carrying in Kallithea is indeed from
the excanvas era of flot.

$ (cd /tmp; \
svn -r 135 checkout http://flot.googlecode.com/svn/trunk/ flot )
$ cp /tmp/flot/excanvas.js rhodecode/public/js/excanvas.js

I also verified the sha256sum of the min file matched ours:

$ sha256sum /tmp/flot/excanvas.min.js rhodecode/public/js/excanvas.min.js
5f94b032a110504b7b261eaf71392fa3e8d82cdc6455c0cba5c9f03cd34ed122 /tmp/flot/excanvas.min.js
5f94b032a110504b7b261eaf71392fa3e8d82cdc6455c0cba5c9f03cd34ed122 rhodecode/public/js/excanvas.min.js