fix(gen): Fix skip-install logic - argument handling now works. Enables dependency installations without internet connectivity / fast.

The skip-install argument handling was not working and has been fixed. By generating an app with the skip-install option: ```yo openui5 skip-install```, we can then manually install our node dependencies.This enables us to do it in offline mode. This is very handy as you do not have to hit and download from the npm registry every single time - if the dependencies are in the cache they are simply re-used.
Run the installs like so:
```
bower install
npm install --cache-min 9999999
```

If you want to check for new versions again just run ```npm install```.