pybullet, more robust multi-server connections

Windows shared memory: allow to use custom key.
Improve GUI performance on Windows, submit letters in text as a batch (fewer draw-calls)
quadruped.py: first try to connect to SHARED_MEMORY, if it fails (<0) use GUI
increase Chrome about://tracing json export capacity (press 'p' in Example Browser)
UDP physics server: add --port and --sharedMemoryKey command-line arguments
PhysicsServerExample: add --sharedMemoryKey command-line option (for VR example too)
ExampleBrowser: sleep a few milliseconds if rendering is too fast, use --minUpdateTimeMicroSecs=0 to disable

examples/SharedMemory/PhysicsServerCommandProcessor.cpp

@@ -1044,6 +1044,7 @@ bool PhysicsServerCommandProcessor::loadSdf(const char* fileName, char* bufferSe
 bool PhysicsServerCommandProcessor::loadUrdf(const char* fileName, const btVector3& pos, const btQuaternion& orn,
                              bool useMultiBody, bool useFixedBase, int* bodyUniqueIdPtr, char* bufferServerToClient, int bufferSizeInBytes)
 {
+	BT_PROFILE("loadURDF");
 	btAssert(m_data->m_dynamicsWorld);
 	if (!m_data->m_dynamicsWorld)
 	{