CSSTUDIO-3461 Simplify naming of configuration option.

Author: abrahamwolk

core/ui/src/main/java/org/phoebus/ui/Preferences.java

@@ -93,8 +93,8 @@ public class Preferences
     /** cache_hint_for_picture_and_symbol_widgets */
     @Preference public static String cache_hint_for_picture_and_symbol_widgets;
     @Preference public static boolean save_credentials;
-    /** phoebus_documentation_path */
-    @Preference public static String phoebus_documentation_location;
+    /** documentation_location */
+    @Preference public static String documentation_location;
 
     static
     {

core/ui/src/main/java/org/phoebus/ui/help/OpenHelp.java

@@ -62,8 +62,8 @@ public Void call()
 
     public static String determineHelpLocation()
     {
-        if (!Preferences.phoebus_documentation_location.isEmpty()) {
-            return Preferences.phoebus_documentation_location;
+        if (!Preferences.documentation_location.isEmpty()) {
+            return Preferences.documentation_location;
         }
 
         final File phoenix_install = Locations.install();

core/ui/src/main/resources/phoebus_ui_preferences.properties

@@ -178,4 +178,4 @@ cache_hint_for_picture_and_symbol_widgets=
 save_credentials=false
 
 # Location of the Phoebus documentation
-phoebus_documentation_location=
+documentation_location=