Support to Select Location from User property for user having Multiple Location Access

Reference Application uses the user User property Location as Default one and allows the user to Login without choosing any Location. Its gets the User Property and checks it whether a valid location or not and then allows the user to Login. 

Enhancing the LBAC module by adding multiple locations access to user and storing them as a list in the user property. So validating the user property as a Location fails and doesn't allow the user to Login having Location User Property.

Changes To Be Made: 

• Check whether Location user Property exists.
• if Exists set the first Location in the List as the session Location and allow  Login

Work needed Here 

https://github.com/openmrs/openmrs-module-referenceapplication/blob/37669c7f027680eb73b7b99535a79d6e44aae69d/omod/src/main/java/org/openmrs/module/referenceapplication/page/controller/LoginPageController.java#L237