Feature: add support for firefox developer edition

I'm using Firefox Developer Edition to develop my applications and I have noticed that Cordova does not support this version, only the normal firefox. Would be great to have this as well. The command I run atm:

```
ionic cordova run browser --buildConfig=build.json --target='firefox developer edition' --livereload --debug --source-map
```

Reproduce the issue with the supplied `ionic cordova run browser` command and target value, then trace how the browser platform handles `--target`. Done means the command recognizes Firefox Developer Edition and launches it with the shown livereload, debug, and source-map options.

Written by the indexing model from the issue text.