restructure the header files

[jupyter-xeus]

restructure the header files

[MCWertGaming]

I have looked at the BaseTerminal and terminal classes and have thought about maybe split the classes into one class for preparing the terminal (base.hpp) and three functions for the input (input.cpp). The thing about moving the input into another files would be that the Windows class could call the preparation class itself int it's constructor and store it's object as private member. that would mean the user don't have to include both window.hpp and base.hpp.

The input class could be made into just functions and put into input.hpp. That would mean that we don't have to pass the object all the time to get user input. Also we don't have to include base.hpp all the time beacuse it needs to hold the Terminal class.

What do you think @certik? Is that a good idea or rather do a different approach here?

[MCWertGaming]

Fixed in #132.