Parse / transform query parameters to the expected builtin types

Summary:
This actually has a bunch of stuff. First:
 - made transform functions for Date and Number. You set up a parameter to be validated as Number or Date, that's how you get it in the handler.
   instead of string
 - the EPBase validate functions were faking async. Truth is they're not really async, nor were they running async. cleaned that up.
 - EPBase has a "setParameters" function that sets params up in the way that the get/post endpoint factories do - with createParamObjects

Test Plan:
made an endpoint with 2 Date params (well.. unix timestamps, but set them up as Date). Handler gets the as Date objects (req.query.start / req.query.end are Date objects).
Also, used setParameters with it.

Reviewers: dougli

CC: SeanDunford, steph

Differential Revision: http://phabricator.palinka.me/D1469