Drop all use of "pcinput" module

[pdawyndt]

The pcinput module has been written to support the user entering correct input during an interactive session.

However, this has little relevance in the context of the online version of the book. Therefore, we could opt to drop all references/use cases of the pcinput module.

We then could also discard the corresponding appendix that explains module and gives its code.

[ppareit]

I came here to ask why the following code
from pcinput import getFloat
gives me an error.

The module pcinput is explained both in the pdf as on Dodona. So the student will expect this to work. Keep in mind that a good workflow for the students is to use the sandbox while writing the code. So minimal interactive use is available.