cavern: improve README

cavern/README.md

@@ -54,12 +54,8 @@ A `cavern.properties` file in /config is required to run this service.  The foll
 # service identity
 org.opencadc.cavern.resourceID = ivo://{authority}/{name}
 
-# (optional) container nodes in the root are allocations:
-org.opencadc.cavern.allocation = /
-
-# (optional) container nodes in /foo and /bar are allocations:
-#org.opencadc.cavern.allocationParent = /foo
-#org.opencadc.cavern.allocationParent = /bar
+# (optional) identify which container nodes are allocations
+org.opencadc.cavern.allocationParent = {top level node}
 
 # base directory for cavern files
 org.opencadc.cavern.filesystem.baseDir = {persistent data directory in container}
@@ -86,9 +82,9 @@ is owned by a user (uisually different from the _rootOwner_ admin user) who is r
 and all conntent therein. The owner of an allocation is granted additional permissions within their 
 allocation (they can read/write/delete anything) so the owner cannot be blocked from access to any content
 within their allocation. This probably only matters for multi-user projects. Multiple _allocationParent_(s) may
-be configured to organise the top level of the content (e.g. /home and /projects). Paths configurted to be 
+be configured to organise the top level of the content (e.g. /home and /projects). Paths configured to be 
 _allocationParent_(s) will be automatically created (if necessary), owned by the _rootOwner_, and will be
-anonymously readable (public). 
+anonymously readable (public). Limitation: only a single level of top-level _allocationParent_(s) are supported.
 
 The _filesystem.baseDir_ is the path to a base directory containing the `cavern` nodes/files.