cfdisk: support partitions list longer than screen LINES

Signed-off-by: Karel Zak <kzak@redhat.com>
cfdisk:add page down/up

Signed-off-by: Karel Zak <kzak@redhat.com>
cfdisk: add usage() and some basic main() stuff

Signed-off-by: Karel Zak <kzak@redhat.com>