Refactor man page whatis entries.

[sorenstoutner]

Debian has a lint checking system named lintian that checks for common packaging problems. One of the warning it produces relates to man pages.

W: litecoin-qt: useless-whatis-entry [usr/share/man/man1/litecoin-qt.1.gz]
N: 
N:   The whatis entry for this manual page (the brief description found in the
N:   NAME section) is of the form:
N:   
N:    program - manual page for program
N:   
N:   This conveys no information about what the program is for and is
N:   repetitive. The short description should contain brief information about
N:   what the program is for to aid in searching with apropos and similar
N:   programs.
N:   
N:   If this manual page was generated by help2man, use the -n option to
N:   provide a more meaningful description.
N: 
N:   Visibility: warning
N:   Show-Always: no
N:   Check: documentation/manual
N:   Renamed from: manpage-has-useless-whatis-entry

The following PR matches a temporary patch I am carrying in the Debian packaging to resolve this issue. I selected a possible short description for each man page, but there may be better options.