Cleanup of ImageSequencer

Added caching to playbook loading
Increased performance of playbook loading
Added default placeholder image

src/engine/openspaceengine.cpp

@@ -95,7 +95,6 @@ OpenSpaceEngine::OpenSpaceEngine(std::string programName)
     , _syncBuffer(nullptr)
 {
 	SpiceManager::initialize();
-	ImageSequencer::initialize();
 	Time::initialize();
 	FactoryManager::initialize();
 	ghoul::systemcapabilities::SystemCapabilities::initialize();
@@ -197,6 +196,8 @@ bool OpenSpaceEngine::create(int argc, char** argv,
 		}
 	}
 
+    ImageSequencer::initialize();
+
 	// Create the cachemanager
 	FileSys.createCacheManager(absPath("${" + constants::configurationmanager::keyCache + "}"));
 	_engine->_console->initialize();