implement repo.logo and repo.logo-link

Allow for per repo logo and logo-link; Use global logo and logo-link per
default.

Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>
Signed-off-by: Lars Hjemli <hjemli@gmail.com>

cgit.h

@@ -70,6 +70,8 @@ struct cgit_repo {
 	char *readme;
 	char *section;
 	char *clone_url;
+	char *logo;
+	char *logo_link;
 	int snapshots;
 	int enable_log_filecount;
 	int enable_log_linecount;