Add [cmd:allowinclude]

Pages must specify whether they want to be included or not.

Otherwise there too many surprises possibe, enforcing access
restrictions will get more complicated

dynamic/dynamiccontentincludepage.cpp

@@ -6,7 +6,11 @@ std::string DynamicContentIncludePage::render()
 	auto rev = revisionDao->getCurrentForPage(this->argument);
 	if(rev)
 	{
-		return rev->content;
+		/* Quite dirty */
+		if(rev->content.find("[cmd:allowinclude]1[") != std::string::npos)
+		{
+			return rev->content;
+		}
 	}
 	return {};
 }

parser.cpp

@@ -148,7 +148,7 @@ std::string Parser::parse(const PageDao &pagedao, UrlProvider &provider, const s
 	std::string result;
 	// we don't care about commands, but we nevertheless replace them with empty strings
 	std::regex tagfinder(
-		R"(\[(b|i|u|li||ul|ol|code|blockquote|img|link|wikilink|h\d|cmd:visible|cmd:rename|cmd:redirect|cmd:pagetitle|category|dynamic:postlist|dynamic:includepage|dynamic:getvar|dynamic:setvar)*?\]((\s|\S)*?)\[/\1])");
+		R"(\[(b|i|u|li||ul|ol|code|blockquote|img|link|wikilink|h\d|cmd:visible|cmd:rename|cmd:redirect|cmd:pagetitle|cmd:allowinclude|category|dynamic:postlist|dynamic:includepage|dynamic:getvar|dynamic:setvar)*?\]((\s|\S)*?)\[/\1])");
 	result = utils::regex_callback_replacer(
 		tagfinder, content,
 		[&](std::smatch &match)