Catalogs:-set.xml files cam exclude themselves

Re-add the old feature, that -set.xml files can explicitly opt-out of
being included in the catalog. Useful for some development and helper /
included files in some aircraft.

catalog/catalog.py

@@ -35,6 +35,11 @@ def scan_set_file(aircraft_dir, set_file, includes):
     if sim_node == None:
         return None
 
+    # allow -set.xml files to specifcially exclude themselves from
+    # the creation process, by setting <exclude-from-catalog>true</>
+    if (sim_node.getValue("exclude-from-catalog", False) == True):
+        return None
+
     variant = {}
     name = sim_node.getValue("description", None)
     if (name == None or len(name) == 0):

catalog/testData/Aircraft/f16/f16-excluded-set.xml

@@ -0,0 +1,11 @@
+<?xml version='1.0' encoding='UTF-8'?>
+<PropertyList include="f16-common.xml">
+  <sim>
+    <exclude-from-catalog type="bool">true</exclude-from-catalog> 
+    <name>f16-excluded</name>
+    <description>Fine</description>
+    <long-description>Blah blah blah</long-description>
+    <variant-of>f16a</variant-of>
+  </sim>
+
+</PropertyList>