Update documentation with minor fixes (#523)

* Change set to add for registry config
* Change userinit to inituser in config creation

Author: georgiastuart

docs/getting_started/installation.rst

@@ -80,7 +80,7 @@ variables in the config:
 .. code-block:: console
  
 
-    $ shpc config set registry:/<DIR>
+    $ shpc config add registry:/<DIR>
     $ shpc config set module_base:/<DIR> 
     $ shpc config set container_base:/<DIR> 
 

docs/getting_started/user-guide.rst

@@ -132,7 +132,7 @@ take preference over this one as follows:
 
 .. code-block:: console
 
-    $ shpc config userinit
+    $ shpc config inituser
 
 
 When you create a user settings file (or provide a custom settings file one off to