Add Settings api, and xpathCompression setting for Android

Same as last, time, you need to use my fork of wd.js to run the tests...
Get/Set doesn't avoid aync altogether, but in the Get/Set is much simpler.  Furthermore, I'm not convinced it's even cleaner.  I think we're bloating the necessary code several times while also introducing extra indeterminacy (ie, when will the proxy get fired?  In the get/set, we know, with event emitter, we do not).