tag-{id}.php template

[ramiy]

ticket #10614 added to wp2.9 a new tamplate file category-{slug}.php. now we have:

1. category-slug.php
2. category-id.php
3. category.php

but on tags tamplate file, the tag-{id}.php is missing:

1. tag-slug.php
2. tag.php

the tag-{id}.php template file is very useful for non-english users, because the tag-{slug}.php contans gibberish letters (hebrew letters in my case). Adding tag-{id}.php will make it easier.

(In [12010]) Allow for tag templates to be linked by tag id as well as name. Fixes #10868.