Script for easy deployment to build server

[johnnyman727]

We need a script that can:

• Compile OpenWRT
• Rename the binary from openwrt-ramips-mt7.... to openwrt.bin
• Put the binary along with the firmware binary into a folder (firmware bin should be named firmware.bin)
• Compress that folder into a .tar.gz
• Name the compressed file the commit SHA of the OpenWRT build (with the .tar.gz file extension)
• Send that up to builds.tessel.io/t2/firmware/
• Set the permissions on that file such that anyone can download it
• Update the builds.json file at `builds.tessel.io/t2/firmware/builds.json by adding the following properties:

'{OPENWRT_COMMIT_SHA}' : {
  "released" : {CURRENT_DATE_STRING},
  "version" : {PREVIOUS_VERSION + 1}
}

• Set the permissions on that folder so that anyone can download it

[johnnyman727]

Fixed with https://github.com/tessel/t2-release