Added new use_distribution_postgresql variable to README.md. Also renamed...

Added new use_distribution_postgresql variable to README.md. Also renamed postgresql_version variable to external_postgresql_version

README.md

@@ -160,7 +160,7 @@ database_user: irodsdb
 # iRODS
 
 irods_version: from 4.2.0 to 4.2.8
-use_local_mirror: false
+use_local_mirror: true or false
 path_to_data: /irods/data
 path_to_icat: /irods/icat
 irods_zone: TESTZONE
@@ -169,7 +169,8 @@ database_name: ICAT
 
 # Misc
 
-postgresql_version: from 9.4 to 13
+external_postgresql_version: from 9.4 to 13
+use_distribution_postgresql: true or false
 selinux_mode: enforcing or permissive
 ...
 ```