add a template tag to output contents of an existing block

[edrex]

see #4529

We want a tag to allow reuse of existing blocks, for instance to output the page title in multiple places.

[Malcolm Tredinnick]

This looks like an exact duplicate of #4529. We have a procedure for what to do if you want to reopen a ticket that has been wontfixed (read contributing.txt for details) and since there's already a lot of history and discussion recorded in the earlier ticket (not all of it unfavourable), I'm going to close this as a duplicate of that one.

[(none)]

Milestone post-1.0 deleted