85 user login spring security

- Add log in mechanism to navbar, with ajax POST
- Spring Security uses UserDetailsService to get Expert from DB via ExpertService and convert to a PublicSiteUser
- Password encoder is Spring Security's implementation of jBCrypt
- beans.xml split into abraid-servlet-beans.xml and applicationContext.xml, to separate the webby beans (handled by DispatcherServlet in web.xml) from middle tier beans (handled by ContextLoaderListener in web.xml) ie in different contextConfigLocations
- Note also: IndexController replaced by AtlasController, and DataValidationController added