Memfile support for Lease Limits
Add the functionality to support lease limits to Memfile_LeaseMgr as outlined below:
- Add lease count map(s) to track leases per class and/or subnet
- Ability to update lease limits upon lease events (add, update, delete)
- Ability to refresh lease count map(s) after lease file load
- Add functions to query for and/or test lease counts against a set of limits