initial stepper motor implementation for setting the airgate position

fixed declaration in strings.h, include strings.h, fixed tests

use size_t, lower thresholds for fireOut rule

renamed some variables, fixed and added some comments

simplified and more stable way to determine the state of the fire

keep 18 previous temperature values of the last 3 minutes to compare ...

against the current temperature every 10 seconds instead of comparing
only every 3 minutes, some other changes

put back default configuration values, allow to cancel alerts with keep ...

== true

apply rule warmStart also when fire is burning

enabled rule "tooRich" again since in can be useful, but with higher ...

thresholds

disabled rule "tooRich" because it does not seem to be a good idea to ...

give more air when the combustion is rich

removed dir warm_start and added rule warmStart instead, tweaked and ...

simplified rules again, adjusted and added tests

further improved rules, adjusted tests, added test

some more tweaking of rules and adjusted some tests

fixed/tweaked again the rules

adjusted rules: wait longer for oxygen sensor to be heated up and give ...

it more time to heat up, time out the sensor heater after 15 mins if
there does not seem to be a fire, switch the heater on if it is off and
not faulted and it seems obvious there is a fire burning, decreased the
min. temp the oven is expected to reach to 700°C, consider the fire
burning if it either reached that min. temperature or if lambda is below
2.

commented constants in rules

added fire dir "burning" and "warm_start", initial impl. of rules for ...

warm start, use constants in rules, added assertNull and assertNotNull

initialize prev measurements with current measurements, updated TODO

allow switching to 8 MHz, use bit shift instead of division to calculate ...

time, poll button every 32 ms instead of 16 ms, some other small
improvements, adjusted tests

don't include avr/power.h for now

use enums instead of constants, rename "heating" to "heater"

moved button, beeper and heater pin settings to pins.h, maintain airgate ...

position in rules, added "tooLean" rule, show fire "direction" together
with current measurements

updated exceptions

added test for checking definitions before a "release"

added more tests, make all tests static/private

enable all test classes...

adding tests + some minor cleanup and improvements

missing German translation

added/improved/fixed some tests, some related small fixes and ...

improvements

don't measure, update and display lambda when heating is not ready since ...

these measurements are useless