alis/main: add -showsecret flag to ALIS LIST

This will enable opers with the chan:auspex privilege to view
hidden (+s) channels in ALIS LIST by using the -showsecret flag.
help/default/alis/list: use 'secret' instead of 'hidden'
alis/main: make negation consistent
alis/main: correct missing negation
Merge pull request #325 from lstarnes1024/master

alis/main: add -showsecret flag to ALIS LIST