Add optional page title prefix/suffix option

Problem/Motivation

A current problem is that the title tag cannot be replicated into other meta tags as-is because it is normally suffixed by the site name, whereas most other title tags don't want that. Partly because of this it is common for content editors to remove the suffix, not realizing the "mistake" they've made.

Proposed resolution

Split the page title in two - the title and the suffix. Add add global separator option.

Incidentally this mirrors the functionality from Nodewords.

Remaining tasks

Determine the best way of implementing this.

User interface changes

TBD.

API changes

TBD.

Data model changes

TBD.