update alarm severity comment and doc

Author: tynanford

app/display/editor/doc/rules.rst

@@ -44,14 +44,16 @@ of the rule are accessible in the expression.
 
 - A PV severity value is referenced using the syntax pvSev{index}, e.g. pvSev0 == 1. Severity values are:
 
-    - -1 - Invalid
-
     - 0 - OK
 
     - 1 - Minor
 
     - 2 - Major
 
+    - 3 - Invalid
+
+    - 4 - Undefined
+
 Value as Expression
 -------------------
 

app/display/runtime/src/main/java/org/csstudio/display/builder/runtime/script/PVUtil.java

@@ -202,7 +202,7 @@ public final static long getTimeInMilliseconds(final RuntimePV pv) throws NullPo
 
     /** Get alarm severity of the PV as an integer value.
      *  @param pv PV
-     *  @return 0: OK;  1: Major; 2:Minor, -1: Invalid or Undefined
+     *  @return 0: OK; 1: Major; 2:Minor; 3: Invalid; 4: Undefined
      */
     public final static int getSeverity(final RuntimePV pv)
     {