NXP-14945: code review

Format & cleanup (add missing annotations, use Java 7 sugar syntax)
Update to 5.9.6-SNAPSHOT post release
Move com.duosecurity:com-duosecurity-java-client dependencyManagement to org.nuxeo:nuxeo-ecm
Use javax.servlet:javax.servlet-api instead of deprecated javax.servlet:servlet-api
Udpate SCM
In org.nuxeo.duoweb.authentication.DuoFactorsAuthenticator:
- The parameter userIdent is hiding a field from type DuoFactorsAuthenticator
=> parameter removed from method signature in order to use the class field
- Throw declaration and catch of Exception
=> throw LoginException
=> catch LoginException & ClientException to keep the same behavior