Added AuthenticationInterceptor/tests and modified SecurityService

Adding the authentication interceptor required:
* Additions to the module.js file
** push the interceptor on to the $httpProvider during config
** added tests to ensure interceptor is being added to $httpProvider
* Changes to the authenticationService tests to mock the security service during logout tests.
* Changes to the securityService
** added getAuthTokenHeader method and tests to use during request intercept
** removed tests - many of the tests were no longer required because the interceptor adds the auth token to each request
* AuthenticationInterceptor itself, which checks the security service to determine whether a user is logged in and if so adds their token to the http request using the security service's configured authTokenHeader value