Add modifiers to MobiFlight Configuration

[DocMoebiuz]

So far MobiFlight provided a very static way of modifying values. We had "transform", "compare" and "interpolation" - in this exact static order. With the concept of "modifiers" this will allow for more flexibility in the future:

• The position of the modifier is not fixed
• We can introduce different modifiers to format and manipulate values in many ways

The first additional modifier is "blink" which allows to let any value blink by applying a sequence of ON and OFF. ON and OFF duration can be defined. Other can be used for "padding", "text-alignment", etc.

This PR does not yet provide a UI for Blink. But the configuration can be added

<modifiers>
  <blink active="True" blinkValue=" " onOffSequence="200,200,400,200" />
</modifiers>

This configuration will let the value blink with a sequence of 200ms ON, 200ms OFF, 400ms ON and 200ms OFF.
The value for the OFF is defined by "blinkValue", in this case a space.

fixes #119

Confirmations:

• Transformation, Comparison & Interpolation are now "modifiers" and loaded as a list
• Backward compatibility with existing configs is preserved and the order of the modifiers is T, C, I
• ExecutionManager will simply execute the chain of modifiers
• Modifier logic resides in modifier class implementation, not in Execution Manager anymore
• Unit tests are all update

Breaking Changes:

• Values are internally handled as Float64 by default. A transform with Round or Floor can be explicitly applied if needed.