Add help menu to pgxc_ctl
Add help menu to pgxc_ctl

User can now use "help" command to see a quick help with available commands on
pgxc_ctl command prompt. Most of the information is borrowed from the pgxc_ctl
documentation. But this does help while using pgxc_ctl

arcivanov/postgres-xl,postmind-net/postgres-xl,kmjungersen/PostgresXL,kmjungersen/PostgresXL,arcivanov/postgres-xl,snaga/postgres-xl,postmind-net/postgres-xl,arcivanov/postgres-xl,kmjungersen/PostgresXL,snaga/postgres-xl,arcivanov/postgres-xl,kmjungersen/PostgresXL,snaga/postgres-xl,arcivanov/postgres-xl,postmind-net/postgres-xl,snaga/postgres-xl,kmjungersen/PostgresXL,postmind-net/postgres-xl,arcivanov/postgres-xl,snaga/postgres-xl,postmind-net/postgres-xl