Auto-correct when check_data applies shifts from 0 and 1

[beckyfisher]

The check_data function will apply a shift to ether the x or y data under certain scenarios. Ideally predicted values (and associated NEC, NSEC and ECx estimates) should be corrected for this shift before being returned.

[beckyfisher]

Note this might be tricky for NEC as it is a returned parameter, not a predicted value.

[beckyfisher]

An alternative to providing corrected values would be to simply add the applied correction as an attribute to the bayesnecfit or bayesmanecfit object.

Note also that this is only important for adjustments to x, as these impact the endpoint estimates when they are near zero.