Reimplementation of SourceInputCallbacks into Session

Session should be the object holding the list of inputs parameters (e.g. synchrony) and the list of source callbacks. This also avoids mixing input when copying sources.  Code could be improved but is operational.

Metronome.cpp

@@ -247,6 +247,23 @@ void Metronome::executeAtPhase( std::function<void()> f )
     std::thread( delay, f, timeToPhase() ).detach();
 }
 
+float Metronome::timeToSync(Synchronicity sync)
+{
+    float ret = 0.f;
+    if ( sync > Metronome::SYNC_BEAT ) {
+        // SYNC TO PHASE
+        std::chrono::duration<float, std::milli> fp_ms = Metronome::manager().timeToPhase();
+        ret =  fp_ms.count();
+    }
+    else if ( sync > Metronome::SYNC_NONE ) {
+        // SYNC TO BEAT
+        std::chrono::duration<float, std::milli> fp_ms = Metronome::manager().timeToBeat();
+        ret =  fp_ms.count();
+    }
+    // SYNC NONE
+    return ret;
+}
+
 size_t Metronome::peers() const
 {
     return link_.numPeers();