DeployConfiguration: Make it possible to enable/disable DCs

Allow DCs to be enabled/disabled.

Add infrastructure to target to propagate enabled signals of
BCs, RCs and DCs.

Change-Id: I8ae27a943953228b18e61396a22a2d7a2e4e9694
Reviewed-by: Tobias Hunger <tobias.hunger@nokia.com>

src/plugins/projectexplorer/deployconfiguration.cpp

@@ -94,6 +94,16 @@ DeployConfigurationWidget *DeployConfiguration::configurationWidget() const
     return 0;
 }
 
+bool DeployConfiguration::isEnabled() const
+{
+    return false;
+}
+
+QString DeployConfiguration::disabledReason() const
+{
+    return QString();
+}
+
 bool DeployConfiguration::fromMap(const QVariantMap &map)
 {
     if (!ProjectConfiguration::fromMap(map))