Added basic support for LDAP authentication
Minor changes to LoginController
Added simple loginform and reworked authentication stack

It is possible now to simulate LDAP login by requesting login page manually
but it needs some more internal changes to do all needed stuff for a real
ARSnova login.
Merge branch 'master' into ldap_integration
Merge branch 'master' into ldap_integration
Configure embedded ldap server for testing
Some simple modifications to work with embedded LDAP server
Store spring authentication in security context

If user is successfully logged in, store authentication in security context
else redirect to login page.
Some basic login page style for MLU
Disable LMS connector
Merge branch 'master' into ldap_integration
Merge branch 'ldap_integration' of scm.thm.de:arsnova/arsnova-war into ldap_integration
Merge branch 'master' into ldap_integration
Merge branch 'ldap_integration' of ssh://scm.thm.de/arsnova/arsnova-war into ldap_integration
Merge branch 'master' into ldap_integration

Conflicts:
	pom.xml
	src/main/webapp/WEB-INF/spring/spring-main.xml
Merge branch 'master' into ldap_integration

Conflicts:
	pom.xml
Merge branch 'master' into ldap_integration
Make LDAP login RESTful

LDAP login now returns status codes 200/401 instead of using
redirection.
Correctly state guest authentication

The API returned "ldap" instead of "guest" for guest authentication
before.
Make authentication providers configurable