Adapted the Viewport to inherit from TextWriter for replacing the TextWriter from the Console itself.
Remove the original printLine procedure and renamed print to printLine.
Modified MusicDB module to use printLine instead of print.
Rewrote most part of the Viewport class. The MusicDB module is changed because row and column locations are counted starting with zero.
Fixed a problem with the initialisation of the Viewport when the executable is run directly from the command line.
Fixed an issue with printing on the bottom line of the screen.
Added an enum to limit the number of options to the clearView procedure.
Merge branch 'feature-viewport' into develop
Several merge conflicts solved.