filters: Add propertiesChangedTo

Add a signal match filter for properties changing to a specific
value.

Change-Id: I10f20ba03ae7c629d2c338c7975e0d32d9008e01
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/examples/match2.yaml b/examples/match2.yaml
index 6fb9ff9..8cfa105 100644
--- a/examples/match2.yaml
+++ b/examples/match2.yaml
@@ -13,6 +13,10 @@
           interface: org.freedesktop.DBus.Properties
           member: PropertiesChanged
       filter:
-          name: none
+          name: propertyChangedTo
+          args:
+            - value: xyz.openbmc_project.Testing
+            - value: TestProperty
+            - value: teststring
 
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