srm: Make dcache-core independent of srm-server

To make this possible, I changed how TransferManager generates IDs. It
now uses the TimebasedCounter class. Granularity of the counter is
increased to 1 Mhz, which should be more transfers than we will ever
see for the entire system, and certainly more than any single door or
transfer manager. The counter still allows for about half a million
years before it wraps around.

This change also means that TransferManager will not use a database
unless transfermanagers.enable.log-to-database is set to true.

Target: trunk
Require-notes: yes
Require-book: no
Acked-by: Tigran Mkrtchyan <tigran.mkrtchyan@desy.de>
Acked-by: Paul Millar <paul.millar@desy.de>
Patch: https://rb.dcache.org/r/7234/