Stop populating FlashVars with query strings

1. Stop populating FlashVars with query strings, by deleting from the `params` object any keys that can be found in the URL.

2. Remove `allowDomain("*")` and `allowInsecureDomain("*")`. If necessary, split MediaElement.js into two separate builds: One for CDNs (`flashmediaelement-cdn.swf`) and another one that is more secure by default (`flashmediaelement.swf`).

Sidenote: It would be much easier to contribute here if #688 / #769 are fixed. This is *untested* but this code is based on previous work on other Flash applets.