Made caching functions more resistent to failures.
Review Request #201 - Created March 12, 2012 and submitted
Whenever memcache_set would fail (with a timeout for example), it would raise a PHP warning which would cause termination of the running script. This is why the evaluator has been crashing daily for the past few weeks. Silenced all cache functions with a @ since they already return TRUE or FALSE on success. Changes were made to config.php.sample so that task and round cache key TTLs are larger when using memcached, since the evaluator is able to invalidate changed data. Diff contains a fix from live for determining if the website is running under https when behind a reverse proxy (such as nginx). Most of the diff's changes are lint fixes.