Update the android viewer app and add firefox os app

The new app uses cordova via npm and has a much simpler ui.
The firefox os version still has a bug, which i'm currently fixing, but I pushed this PR for review already since the bug is a regression. Fixing it will not cause a large code change.
The java code is nearly identical to the code in programs/android. The latter will be removed in a new pr when this pr lands.

Taks list:
* [x] build firefox os and android apps without needing dependencies of the other
* [ ] let cmake detect android
* [ ] make WebODF/platforms/firefoxos/build/package.zip a variable, pointing to a file in the toplevel build dir
* [ ] Same with WebODF-debug.apk
* [ ] Check that all new js and java code has licenses
* [ ] Give a helpful message when running in the Firefox OS simulator

`WebODF/config.xml` is also created by the commands for `${CMAKE_CURRENT_BINARY_DIR}/WebODF/hooks/README.md`. So at least on first run for me the Makefiles generated by cmake decide that `WebODF/config.xml` is already up-to-date and thus skip the complete commands listed here. Which results in the errors I reported before about missing icon and bad app description.
A fix which works for me is to instead copy the `config.xml` file also to the `merges` folder to overwrite the cordova-created one. See https://github.com/kossebau/WebODF/commit/22754c3c2989d4b36f50681b3c5cc22dff96bc4b