manifest.json incorrect generation for heli firmwares

This causes QGC to not be able to load heli firmwares on all boards. I'm not sure if it is just "OFFICIAL" versions which are incorrect. But those are the only entries which QGC uses for now.

Here is an example of an incorrect entry:
```
{
"mav-type": "Copter",
"vehicletype": "Copter",
"mav-firmware-version-minor": "6",
"format": "hex",
"url": "http://firmware.ardupilot.org/Copter/stable/CubeBlack-heli/arducopter-heli.hex",
"mav-firmware-version-type": "OFFICIAL",
"mav-firmware-version-patch": "9",
"mav-autopilot": "ARDUPILOTMEGA",
"platform": "CubeBlack-heli",
"mav-firmware-version": "3.6.9",
"git-sha": "632be63f053d45ab584190586d4a028abca9a2e4",
"mav-firmware-version-major": "3",
"latest": 0
},
```
For this one mav-type should be "HELICOPTER" and platform should be just "CubeBlack".

Not all are wrong, here is an example of a correct entry:
```
{
"mav-type": "HELICOPTER",
"vehicletype": "Copter",
"mav-firmware-version-minor": "6",
"format": "arducopter-heli",
"url": "http://firmware.ardupilot.org/Copter/stable/navio-heli/arducopter-heli",
"mav-firmware-version-type": "OFFICIAL",
"mav-firmware-version-patch": "9",
"mav-autopilot": "ARDUPILOTMEGA",
"platform": "navio",
"mav-firmware-version": "3.6.9",
"git-sha": "632be63f053d45ab584190586d4a028abca9a2e4",
"mav-firmware-version-major": "3",
"latest": 0
},
```

No source file, test, or entry point is named. Locate the generator for manifest.json, then compare its heli firmware output with the two examples in the issue. Done means generated heli entries use the expected mav-type and platform values and QGC can load them.

Written by the indexing model from the issue text.