Create a dashboard page for keg line calibration

[thomaskipar]

Please add a new page enter calibration values for each keg line (= zapf kit).

1. Define a REST API to access current calibration data and to change the data
2. Create the dash board page using that API.
3. Assign the issue to me so I can implement the backend corresponding to your API change.

See #88 for back end implementation

[thomaskipar]

The following variables can be adjusted for calibration (linear regression):

• regression (double)
• disturbance (double)
• tick reduction (int)

"tick reduction" is subtracted from EACH tick request (so each tick message sent from the zapf kit to the back end). If x is the amount of ticks sent to the back end, (x-tick_reduction) will be used for all further processing.

"regression" and "disturbance" are the to coefficients for the linear regression to calc the draw amount in liters from total ticks (total ticks is the sum of all ticks collected for a single draw process. Node: each addend was reduced by tick reduction already!). So formula is simply amount = regression * total_ticks + disturbance.

Please also add a meaningful help text to the dash board for all variables.

[partysalat]

Added JSON Schema Concept at https://github.com/just-kile/Zapfmaster2000/wiki/JSON-Schema#dashboard ->Calibration Please verify and, if necessary, edit it.

I implement the dashboard page currently. (Dashboard is available at /zapfmaster2000-service/dashboard/)

[thomaskipar]

Please test :-)

[partysalat]

works!