Update pgbackrest wrapper to support multiple repositories in the selection

ReadMe.md

@@ -25,7 +25,7 @@ This file holds the sudo_user for calling the commands
 
 ```ini
 [PgBackRest]
-sudo_user=pgbackrest
+sudo_user=postgres
 ```
 
 ### `config/stanza.cfg`
@@ -34,8 +34,11 @@ Example file is `stanza.sample.cfg`
 
 This files holds the stanzas to backup
 
+If the stanza has several repo settings as in "repo1-...", "repo2-..." then the repo to target can be listed in here by ":repo number"
+
 ```ini
 [stanzas]
 stanza_a
-stanza_b
+stanza_b:1
+stanza_b:2
 ```