cfdisk: add menu action functions

Signed-off-by: Karel Zak <kzak@redhat.com>
libfdisk: add fdisk_table_get_partition()

Signed-off-by: Karel Zak <kzak@redhat.com>
cfdisk: update menu according to the current partition

Signed-off-by: Karel Zak <kzak@redhat.com>
cfdisk: improve info line, add Delete action

Signed-off-by: Karel Zak <kzak@redhat.com>
cfdisk: improve info line and menu updates

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