To abstract rather complex functions for 7 segment displays e.g. blink text, scroll
text... a class was created.
This makes it possible to have 2 instances for displayTop and
displayBottom resulting in no duplicate code
Fix bug where sartup randomly crasehd several times because spi config
was initialized with random data -> init with 0
Fix bug where length now was not truncated resulting in flickerin
Fix bug in welcome message where hello string contained random data