Clarified the variable and member names, straightened out the code flow, fixes the (crashing) issue with the selections properly.

Also have a separate patch on top of this to move most of the code out of TerminalDisplay (my goal is to get TerminalDisplay.cpp below 3000 lines :-).

Same as the ones from the earlier commits related to this, but no autotests yet (want to wait until the code is in the right place first).