Add a JBoss SSO Login module.

Add a JBOSS SSO Login module that uses REST to connect to a configurable server url.
Configuration happens in standalone.xml and should look something like this:
```xml
<security-domain name="zanata.jbosssso">
     <authentication>
           <login-module code="org.zanata.security.JBossSSOLoginModule" flag="required">
                 <module-option name="serverURL" value="-- server url --"/>
           </login-module>
     </authentication>
</security-domain>
```
I think it would have to be some sort of global (not an instance variable) to achieve any reuse of ObjectMappers, but on second thought it's not worth the ugliness it would require.