fdisk: change primary or extended partition type dialog

fdisk: change primary or extended partition type dialog

Mainly this appends a colon for the prompt, reverses order of the list,
reports the number of primary partitions used and unused.

Old version:
 Command action
    e   extended
    p   primary partition (1-4)
 p

New version:
 Partition type:
    p   primary (0 primary, 0 extended, 4 free)
    e   extended
 Select: p

Old version:
 Command action
    l   logical (5 or over)
    p   primary partition (1-4)
 l

New version:
 Partition type:
    p   primary (0 primary, 1 extended, 3 free)
    l   logical (numbered from 5)
 Select: l

Signed-off-by: Francesco Cosoleto <cosoleto@gmail.com>