pitrtools

Since we position PITRTools as a tool to simplify WAL-shipping and replication setup, I though I'd count the number of options once needs to set in PIRTools, against pristine PostgresSQL:

PITRTools:
Archiver: 15
Standby: 31.

Comparing to the pristine PostgreSQL:
primary: (wal_level, archive_mode, archive_command, max_wal_senders) - 4.

standby (most of them belong to recovery.conf): (hot_standby, standby_mode, primary_conninfo, restore_command, archive_cleanup_command): 5

We need to rethink PITRTools configuration options. I've made the first step by splitting them into required and uncommon, and put reasonable defaults for the second ones (i.e. assumed ssh and rsync path is fixed, and there is no need to tweak rsync options or set ssh_debug), but to make the tool easier than pristine PostgreSQL we need to put some code to autodetect some of the parameters (i.e. autodetect things like PostgreSQL version, checkpoint_segments value for 8.2 and below, rsync_version, etc.)