Add firmware features

[sayanee]

• Record and store IR raw codes, ideal temperature, interval, and duration
• Measuring battery voltage hutscape/hutscape.github.io@ff755a7
  - need test with used batteries
• Sleep and wakeup periodically to check the temperature and turn on/off the aircon
• Display config data from flash if it is already there
• Record any infrared signal and test it on the web UI before confirming which one is correct
• Remove 292 signal length to store variable-length signals

[sayanee]

• implement task with sleeping and wakeup
• fix form validation when IR raw code is added