Upload latest master, beta and stable builds to AWS

[dagar]

I removed the other s3 artifacts upload assuming you don't also want to keep every Firmware.zip on s3.

I uploaded some unnecessary files when attempting to use the travis builtin s3 upload. You could probably delete everything in the bucket at this point and travis will repopulate.

[dagar]

Fixed CI-Tools/s3cmd-put so it only uploads if not a pull request.

[dagar]

hmm the dynamically generated s3 directory index isn't quite right.
http://px4-travis.s3.amazonaws.com/master/index.html

[LorenzMeier]

In fact we do want artifacts for most builds so our testers can download straight from Travis and don't need the tool chain installed.

[LorenzMeier]

I think I'm missing partially context here - the overall state / uploaded material looks good (I cleaned up a bit). I presume we can exchange the flow badge here soon too and call the job done?
http://px4-travis.s3.amazonaws.com/index.html

[dagar]

Sorry, that was not very clear. I was referring to the existing travis addon called artifacts which was already uploading Firmware.zip. https://github.com/PX4/Firmware/blob/master/.travis.yml#L81-L82

One last change to put things in project folders (so we can add px4flow alongside) and this should be good to go. As soon as this is in and working I'll add the few lines to px4flow travis.yml for upload and add the badge.

[LorenzMeier]

Awesome, merging!