Allow blank value for offset on onewire sensor

Fixes bug caused introduced when adding the offset (temps only reading 0)

Change to notification to use message event bus

Allow specifying an offset on onewire sensor

Replace int with float in get_sensor_value()

Allow SQL file to be re-run

Update controller.py

Allow floats for offeset min/max

This will allow any plugin to listen for a notification and respond accordingly.

Allow the schema.sql file to be re-run if it changes

-Brew Steps added
-Clean AddOn Dialog

lines 138 and 144 were changed to f.cooler

I've noticed that sensor values are being handled as integers by this function, which was causing poor performance of the PIDArduino logic and another logic plugin I am testing.  I have changed the type to float, and now logic controllers can receive more accurate temperature values.

Update __init__.py

- Method actor_power added to set the power without switching
- Method timer_remaining added to get the remaining time of a timer

Correct datatypes for def F automode to work

- Fix Autostart
- Add Splash Screen for Pixel

Add GPIO Pin 27

# Conflicts:
#	modules/core/controller.py

- Kettle Controller Fix
- Remove SQL Alchemie

Closes https://github.com/Manuel83/craftbeerpi3/issues/7

Fix exception in FermenterController