GitLab

 - {update,remove}Statistics moved from CfgMgr to SrvConfig,CfgSubnets4

 - Moved MAC operations to a new CfgMACSource class
 - Moved macros to HWaddr class
 - Added several unit-tests for MAC sources
 - MAC extraction code moved to separate function in Dhcpv6Srv

The modifications to the staging configuration are performed on the pointer
returned by getCfgOptionDef.

This change affects many files using the Configuration object and types
derived from it.

Previously, the logger configuration was applied (to log4cplus) as soon as
it was parsed. We decided in the jabber discussion that the logger
configuration should only be applied if the whole configuration goes
through. So, the logger configuration is now 2-stage: parsing and commit
as for other configuration parameters.

This is trivial fix so as I am committing it on my own discretion. Also,
this fix had already been reviewed and applied on master branch but
apparently disappeared after the recent git migration.