Pagefiles::getTag() method

Return the first Pagefile that matches the given tag or NULL if no match

Given tag may be any of the following:

• foo (single tag): Will return the first Pagefile object having the specified tag.
• foo|bar|baz (multiple OR tags): Will return first Pagefile object having at least one of the tags listed.
• foo,bar,baz (multiple AND tags): Will return first Pagefile object having ALL of the tags listed (since 3.0.17).
• ['foo','bar','baz'] (multiple AND tags array): Same as above but can be specified as an array (since 3.0.17).