Exception handling, logging and cleanup

Moved coffee_pot class to its own file; removed internal refs
Added logging support to coffeepi_controller
Added logging support to coffee_pot
Renamed serial lcd class and code file
Cleaned up imports in coffeepi_controller
Exception handling in coffeepi_controller
Reading data clipping when above/below max/min
Removed current_level and fixed typo in postvalue props in coffee_pot
class
Set lastbrew time to > 24h before to force OLD display on startup
Added comments to coffee_pot with suggestions for fixes