Rewrite shell scripts to JS

[NeoLegends]

Current installation shell scripts sometimes have trouble with execution rights. Cordova is able to execute JS files instead of shell scripts on installation time, though. They're less likely to have these problems.

Extracted from #21 . Closes #21.

[andreasseiler]

👍

[NeoLegends]

@andreasseiler Please make use of the 👍🏻-emoji on the issue comment instead of posting +1s. This keeps the tracker clean. :)

[NeoLegends]

Hmm, all the shell scripts have the execute permission set.