lscp: show block count by default

For each checkpoint of NILFS2, total block count (BLKCNT) is more
meaningful information than appended block count (NBLKINC).  This
changes the default display information of lscp command on block count
to BLKCNT from NBLKINC, and updates relevant man pages.  NBLKINC can
be still displayed when we specified '-g' option.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>