Inconsistencies between GUI and TUI in SUPERVISOR:
1) add the possibility to create of an InLine node without a
Python function defined (empty, no code);
2) add the possibility to define Python functions in EndLoop and EndSwith
nodes and to create Loop and Switch nodes with empty functions;
3) add the possibilyty to define a function without a body - in this case,
if a function with the same name was already defined in another node,
it's code (body) will be used (executed).
