Create log list / information field for the GUI.

The GUI should have a field for error / information output. This log list should print given messages to the GUI.
This includes the functionalities:

• print information messages like file opened/closed, graph updated etc.
• print error message like no such file, etc (maybe in red?)
• print success messages like τ calculated, file successfully saved (maybe in green?)
• reset/clear the log
• the log should be scrollable