ikiwiki: Disable discussion pages by default for new wiki/blog

Closes: #2102.

- Wiki: Unchanged behavior is to have discussion pages enabled. To post users
must login.

- Blog: Earlier behavior is to allow anonymous users to post comments. They go
into the moderation queue when posted. This could lead to a lot of spam comments
to moderate. New behavior is to allow posting comments only when logged in.

- Blog: discussion => 0 does not effect comments. It is meant for discussion
page on the blog's home page (and possibly other pages). Discussion on those
pages is disabled by default.

- The changes only apply to defaults. Everything can be changed from Setup page.

Testing:

- Test the above described behavior in Debian testing.

- Debian stable testing was not done as the version of ikiwiki is that same as
testing.

[sunil: Drop removal of discussion from wiki pages]
Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: Sunil Mohan Adapa <sunil@medhas.org>

plinth/modules/ikiwiki/data/usr/share/freedombox/etc/ikiwiki/plinth-blog.setup

@@ -25,7 +25,7 @@ IkiWiki::Setup::Automator->import(
     cgiurl => "/ikiwiki/$wikiname_short/ikiwiki.cgi",
     cgiauthurl => "/ikiwiki-auth/$wikiname_short/ikiwiki.cgi",
     cgi_wrapper => "/var/www/ikiwiki/$wikiname_short/ikiwiki.cgi",
-    add_plugins => [qw{goodstuff websetup comments calendar sidebar trail httpauth lockedit opendiscussion moderatedcomments userlist remove attachment}],
+    add_plugins => [qw{goodstuff websetup comments calendar sidebar trail httpauth lockedit moderatedcomments userlist remove attachment}],
     rss => 1,
     atom => 1,
     syslog => 1,