[TIMOB-16657] Allow for non-timestamped builds on http://builds.appcelerator.com/#3.2.3

So I've created a Jenkins script to tag and upload alpha/beta/rc builds to S3. I figure the best place is where we currently upload the nightlies, but in a different stream. However, http://builds.appcelerator.com/#3.2.3 doesn't work because 3.2.3.Alpha1 fails this regex:

var p = build.filename.match(/^mobilesdk\-(.+)(?:\.v|\-)((\d{4})(\d{2})(\d{2})(\d{2})(\d{2})(\d{2}))\-([^\.]+)/),
ts = p[2];

I need a fallback mechanism for communicating the build's timestamp as part of index.json, where the build itself doesn't contain a timestamp. Alternately, we could suffix the alpha1 with the timestamp, but I'm not sure how clean that would look.