IrSenderNonMod should have inverting option

[bengtmartensson]

Use case: for example, using IrSenderNonMod to emulate the output of a demodulating receiver; these are (almost?) always active low.

Possible implementation:

private:
    bool inverting;

public:
     IrSenderNonMod(pin_t pin, bool inverting_ = false) : ... inverting(inverting_) { ... } 

Alternative: derived class IrSenderNonModInvert. (Boolean arguments are considered evil these days ;-).)