Add support for processing signal event triggers

Process signal event triggers' list of conditions on a group and perform
the defined actions.

This re-uses the following struct directly from
phosphor-inventory-manager:
--struct PropertyChangedCondition

Change-Id: I98552f3d168cfcd9f0c1c357289b7000374ae60e
Signed-off-by: Matthew Barth <msbarth@us.ibm.com>
diff --git a/src/monitor.hpp b/src/monitor.hpp
index aca64d8..5256582 100644
--- a/src/monitor.hpp
+++ b/src/monitor.hpp
@@ -30,6 +30,12 @@
                          const std::tuple<std::vector<std::shared_ptr<Event>>,
                                     std::vector<Action>>& eventDef);
 
+        using eventArg = std::tuple<Monitor*,
+                                    const SignalEvent*,
+                                    const std::tuple<
+                                        std::vector<std::shared_ptr<Event>>,
+                                        std::vector<Action>>*>;
+
     private:
         sdbusplus::bus::bus& bus;
 
@@ -37,6 +43,14 @@
             std::tuple<std::vector<std::shared_ptr<Event>>,
                        std::vector<Action>>> events;
 
+        std::vector<std::unique_ptr<eventArg>> eventArgs;
+
+        std::vector<sdbusplus::server::match::match> matches;
+
+        static int handleSignal(sd_bus_message* msg,
+                                void* data,
+                                sd_bus_error* err);
+
 };
 
 } // namespace monitoring