[yocto] Changes to the autobuilder.

[Flanagan, Elizabeth]

I've made a few changes to the autobuilder that people should know about. Currently, we've been utilizing the milestone builders to split the nightly to both the internal and external builders in order to speed things up. I've renamed them to nightly-internal* and nightly-external*. They were putting their build output to the milestone directory on the webserver. This was incorrect behavior. I've changed this to make the build output go out to the nightly directory of the webserver: http://autobuilder.pokylinux.org/nightly.

The big change is to how we deal with emenlow, atom-pc, beagleboard, etc. These are now found under the machines/<machine_name>/<arch> directory in the build output web directory. I'll need to eventually refactor some of the autobuilder scripts to deal with BSPs a little more elegantly, but it's functional for now and we have a standard to adhere to.

Also, be aware that we now have a functional CURRENT link, so if you go to the autobuilder/nightly/CURRENT directory this will point to the last thing the autobuilder built. Keep in mind, it will create that link even if the build is broken. 
I'll have a commit with all of this in it when I finish up the upgrade to 0.8.3.

If you have any questions, feel free to ask.

-b