CORE: fixed javadoc in API for getMembers() like methods

- fixed javadoc in API for getMembers(), getRichMembers() and
  getRichMembersWithAttributes() methods in Members/GroupsManager.
  Javadoc described methods using pageNum/pageSize, which are
  long gone.
Merge pull request #101 from zlamalp/core

CORE: fixed javadoc in API for getMembers() like methods