More configurable DOM attributes

I am using ZeroClipboard in a 3rd party JS application. As such it is extremely important we be as defensive as possible, namespace everything, and so on.

I had to make changes to ZeroConfig to accomplish this, and think others might find them useful.

This PR adds three new properties to the global configuration object:
* containerId
* containerClass
* flashBridgeName

The only change this PR introduces is the ability to configure these values. They are optional properties, and default to the values you've been using.