Updates README with actual configuration and notes. (+1 squashed commits)

Squashed commits:

[c9d38ac] updates documentation
Added back logic to update cordova repos instead of re-cloning them
Windows: logic to specify target build version via config

As per cahnges in Windows Universal Apps logic:
* no --store80 switch anymore;
* target version is specified via config.xml:
<preference name="windows-target-version" value="VERSION" />