Check for a CORDOVA_HOME environment variable to create the global config path

I would like the ".cordova" folder not to be created in my HOME folder, but in a custom path, that would be declared in a CORDOVA_HOME environment variable. 

This will be useful for a multi-user environment. Instead of having the same .cordova folder in each user's HOME folder with the same content, I will be able to create a single .cordova folder, that every user will be able to access.