Added dialog for barcode printing

Added dialog for barcode printing with settings.
Merged the barcode gui into mainwindow

Merged the barcode gui into the main window
Cleaned up warnings

Cleaned up warnings about unused variables.
Added printer support

Added printer support with presets to the main window. The barcode
height must still be tested though.
Made dialog modal

Made dialog modal, since it does not make sense to modify it's parent
while the search dialog is active.
Reduced barcode heigth

Reduced the heigth of the barcode and introduced a new static variable
to control the margin between the barcode and the text.