Add callback contexts

Add the notion of a callback context. This enables callbacks
to have logic around the conditions they were invoked in.

There are two context on which call back can be invoked
1) Startup: during startup all the call backs will be called
2) Signal: As part of condition match on the watched properties.

Callback would behave differently based on the context.
eg: eventCallback
1) Startup: Don't take any action.
2) Signal: Create the Dbus Object for the event.

Change-Id: If455558798ac3e44bbd8a93de0ce1b09d2e308ae
Signed-off-by: Ratan Gupta <ratagupt@in.ibm.com>
diff --git a/src/journal.cpp b/src/journal.cpp
index 46f74e9..c348cfb 100644
--- a/src/journal.cpp
+++ b/src/journal.cpp
@@ -22,7 +22,7 @@
 namespace monitoring
 {
 
-void JournalBase::operator()()
+void JournalBase::operator()(Context ctx)
 {
     for (const auto& n : index)
     {