Creates and attaches a new meta-rule caller function to register added meta rules.
After calling add-meta-rule or when different books with meta rules are included, users need to call attach-meta-fncs. This creates a new meta function caller function and attaches it to rp::rp-rw-meta-rule.
(rp::attach-meta-fncs unique-prefix)
unique-prefix should be a unique name that will be a prefix to the name of the new meta-rule caller function.