Support --columns 0 which disables column limiting

[ajakk]

Setting the columns to "unlimited" can be necessary when piping the output of bugz:

pybugz $ ./lbugz search pybugz
 * Info: Using [Gentoo] (https://bugs.gentoo.org/xmlrpc.cgi)
 * Info: Searching for bugs meeting the following criteria:
 * Info:    status               = ['CONFIRMED', 'IN_PROGRESS', 'UNCONFIRMED']
 * Info:    summary              = ['pybugz']
479422 williamh             www-client/pybugz needs templates for new bugs
604826 williamh             www-client/pybugz - bugz search -C Stabilization -C Keywording: UnicodeEncodeError: 'ascii' codec can't encode character '\u2008' in position 55: ordinal not in range(128)
 * Info: 2 bug(s) found.
pybugz $ ./lbugz search pybugz | cat -
 * Info: Using [Gentoo] (https://bugs.gentoo.org/xmlrpc.cgi)
 * Info: Searching for bugs meeting the following criteria:
 * Info:    status               = ['CONFIRMED', 'IN_PROGRESS', 'UNCONFIRMED']
 * Info:    summary              = ['pybugz']
479422 williamh             www-client/pybugz needs templates for new bugs
604826 williamh             www-client/pybugz - bugz search -C Stabilization -C
 * Info: 2 bug(s) found.
pybugz $ ./lbugz --columns 0 search pybugz | cat -
 * Info: Using [Gentoo] (https://bugs.gentoo.org/xmlrpc.cgi)
 * Info: Searching for bugs meeting the following criteria:
 * Info:    status               = ['CONFIRMED', 'IN_PROGRESS', 'UNCONFIRMED']
 * Info:    summary              = ['pybugz']
479422 williamh             www-client/pybugz needs templates for new bugs
604826 williamh             www-client/pybugz - bugz search -C Stabilization -C Keywording: UnicodeEncodeError: 'ascii' codec can't encode character '\u2008' in position 55: ordinal not in range(128)
 * Info: 2 bug(s) found.