Support reloading server configuration file

[m-ronnblom]

Support changing server configuration in runtime (without a server restart). An example would be changing the debug filtering level from 'info' to 'debug'.

Certain configuration changes may require disconnecting clients and discarding domain state. For example, lowering the administrative limit for a certain resource to a value which is less than what is already used might be difficult to handle, Pathfinder protocol wise

The re-reading could be triggered by a USR1 signal, as per the UNIX daemon tradition.