3808 Change wording on mergers and add links

https://code.google.com/p/otwarchive/issues/detail?id=3808

>If possible, the sentences could be changed to:

>[tag-name] has been made a synonym of [linked canonical tag-name].
Works and bookmarks tagged with [tag-name] will show up in [canonical tag-name]'s filters.

>with [linked canonical tag-name] linking to the canonical tag in question?