AC2: Implement whoami entry.

...rol-Server/src/ca/nrc/cadc/ac/server/UserPersistence.java

...ol-Server/src/ca/nrc/cadc/ac/server/ldap/LdapUserDAO.java

...r/src/ca/nrc/cadc/ac/server/ldap/LdapUserPersistence.java

...rver/src/ca/nrc/cadc/ac/server/web/users/UsersAction.java

...c/ca/nrc/cadc/ac/server/web/users/GetUsersActionTest.java

...adcAccessControl/src/ca/nrc/cadc/ac/client/GMSClient.java

...ca/nrc/cadc/ac/client/JSONUserListInputStreamWrapper.java

...adcAccessControl/src/ca/nrc/cadc/ac/json/UsersWriter.java

...cadcAccessControl/src/ca/nrc/cadc/ac/xml/UsersWriter.java

...Control/test/src/ca/nrc/cadc/ac/client/GMSClientTest.java

...rc/cadc/ac/client/JSONUserListInputStreamWrapperTest.java