docs(angular.module): improve docs
docs(angular.module): improve docs

it wasn't clear before that if given the same name a second time this method RETRIEVES an EXISTING module.  Not even sure if my description is accurate, hoping someone will either confirm and merge or clear it up.

Closes #3666

ammula88/angular.js,ammula88/angular.js,ammula88/angular.js,ammula88/angular.js,ammula88/angular.js