QPID-4054 C++ Broker connection limits per user
1. Constrain maximum limits to be a few ticks below Uint16_t max to avoid inadvertent wrapping and to allow room for some named constants such as UNLIMITED.
2. Add syntax to Acl rule file
   quota connections N user|group [user|group]
3. Pseudo user 'all' receives value from command line switch or from Acl rule file.
4. Named constant strings used in comparisons instead of local strings.
5. Connection counts maintained all the time to support reolad of Acl rule file that may change limits.
6. Self tests exercise all the features.



git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1444302 13f79535-47bb-0310-9956-ffa450edef68