show: Rework show procedure

Added

 - ability to parse every single file crtools
   understands via magic number

 - dumped memory pages can be rendered in two
   modes -- as a simple set of pages' virtual addresses
   or in hexdummp fashion (via -c command line key).

For example

  ./crtools -s -c -f pages-2557.img

CR_FD_PAGES: pages-2557.img
----------------------------------------
    7fffb44ace20: 00 00 00 00 00 00 00 00  00 00 00 74 65 73 74 2f  |. . . . . . . .  . . . t e s t / |
    7fffb44ace30: 74 65 73 74 2d 73 69 67  61 63 74 69 6f 6e 00 48  |t e s t - s i g  a c t i o n . H |
    7fffb44ace40: 4f 53 54 4e 41 4d 45 3d  6c 6f 63 61 6c 68 6f 73  |O S T N A M E =  l o c a l h o s |
    7fffb44ace50: 74 2e 6c 6f 63 61 6c 64  6f 6d 61 69 6e 00 54 45  |t . l o c a l d  o m a i n . T E |

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>