Use percentage-based width for the sidebar
Use percentage-based width for the sidebar

Use percentage-based widths internally. This slightly impairs (user)
feedback but brings the sidebar configuration menu closer to the actual
configuration format (the user now configures percentage-based widths,
not absolute width values). As a bonus, the sidebar is now resized
automatically on each window resize (based on the percentage values).

Signed-off-by: Lukas Fleischer <af90e31281d8305af43dc616c5aaca3c7165f8a7@cryptocrack.de>

lfos/calcurse,lfos/calcurse,lfos/calcurse