review: saved replies

[jamierocks]

As discussed on SPORE

Implement a saved reply system, to allow plugin reviewers to store review comments for plugin developers.

Ideally there would be a local set (specific to the reviewer), and a global set (available to all reviewers). Also ideally they'd be a tree (e.g. documentation->external downloads, or dependencies->legacy bstats).

[Katrix]

To further elaborate on this. My initial goal for this is globally hardcoded defined messages which can be localized. Further down the road it shouldn't be too hard to open this up to other messages globally. User-specific stuff would probably come later.

Regardless, this would need the messages table described in #707