* Move the release build steps into separate shell scripts
* Remove builds that we don't need any more
* Latest builds of er9x and erSkyTx both support MULTI_TELEMETRY so separate OpenTX / erSkyTx builds are no longer needed
* Radio can switch telemetry inversion on or off automatically so STM32 inv / noinv builds are no longer needed
Various improvements to the Travis CI script:
* Add channel order builds to releases - now building AETR, TAER, and RETA
* Add PPM builds for each channel order with no inversion and PPM banks set to 5
* Log config diff for each build (diff output folded to keep the log readable)
* Colorify the "Building" lines to make parsing the log easier
* Export .bin files instead of .hex files for the AVR modules
* Add Multi.txt to the release files
* Use latest STM32 board options
* Use latest Arduino IDE
* Fix build functions to return an error if the build fails
* Modify the files that get exported to releases
* Change build commands to make log a little easier to read
* Create a backup of the _config.h file before starting
* Add `before_deploy` and `deploy` sections to deploy compiled binaries when a release is tagged
