Rewrite to reduce memory usage and add more features

In addition to the clock scene, both the animation scene and the weather
scene should now work under MicroPython on devices with 520kBytes of RAM
(e.g. LoPy 1, WiPy 2) after:

- combating heap fragmentation during initialization by temporarily allocating
  a large chunk of RAM in the beginning of main.py and freeing it after all
  modules have been imported and initialized
- stream parsing the JSON response from the weather API
- converting animations to binary and streaming them from the flash file system

(additionally, older ESP8266 modules with 4MB flash have been found working
 under some circumstances with MicroPython 1.9.4 and an 8x8 LED matrix)

- 3D parts: add diffuser grid and frame for square LED matrix displays
- Arduino projects needs to be in a folder with the same name as the .ino file
- config: allow multiple WiFi networks to be configured
- config: add support for debug flags
- config: add intensity configuration
- HAL: unify serial input processing for Arduino and Pycom devices
- HAL: handle UART write failures on Pycom devices
- HAL: drop garbage collection from .update_display() because it takes several
  hundred milliseconds on 4MB devices
- MCU: clear display when enabling/disabling MCU independence from host
- PixelFont: move data to class attributes to reduce memory usage
- PixelFont: add more characters
- PixelFont: move data generation to scripts/generate-pixelfont.py
- LedMatrix: support LED matrixes with strides other than 8 (e.g. as 16x16 matrices)
- LedMatrix: add method to render text
- LedMatrix: let consumers handle brightness themselves
- AnimationScene: MicroPython does not implement bytearray.find
- AnimationScene: ensure minimum on-screen time
- BootScene: wifi connection and RTC sync progress for Pycom devices
- ClockScene: delete unused code, switch to generic text rendering method
- FireScene: classical fire effect
- WeatherScene: bug fixes, switch to generic text rendering method
- WeatherScene: ensure minimum on-screen time
- WeatherScene: use custom JSON parsing to reduce memory usage

arduinoserialhal.py

@@ -7,6 +7,7 @@
 # or under MicroPython.
 #
 import serial
+import time
 
 class ArduinoSerialHAL:
 	"""
@@ -17,12 +18,15 @@ class ArduinoSerialHAL:
 	def __init__(self, config):
 		self.port = config['port']
 		self.baudrate = config['baudrate']
+		self.tz_adjust = config['tzOffsetSeconds']
 		self.ser = None  # initialized in reset()
 		self.reset()
 
-	def readline(self):
+	def process_input(self):
 		"""
-		Read output from MCU over the serial link
+		Process data coming from the MCU over the serial link, such as any
+		captured button presses by the firmware or log messages, and return
+		it as input data to the caller (the main game loop)
 		"""
 		if not self.ser.in_waiting:
 			return None
@@ -39,6 +43,7 @@ class ArduinoSerialHAL:
 		print('SerialProtocol: opening port {} @ {} baud'.format(self.port, self.baudrate))
 		self.ser = serial.Serial(self.port, baudrate=self.baudrate, rtscts=True, timeout=0.1, write_timeout=0.5)
 		self.resynchronize_protocol()
+		self.set_rtc(int(time.time()) + self.tz_adjust)
 
 	def resynchronize_protocol(self):
 		"""