Changed behaviour of generating new nodeid.

• Previous solution did clone with nodeid 100, which was also then used in replicationslot name which ended up in recovery.conf.
  That solution didn't work with more than one standby, since they both wanted to replicate using same replication slot.
  New solution is a complex python script that finds master, detects a free nodeid, registers it immediately and then uses that for cloning.
  New solution works with multiple standbys too.