Add expensive parser functions {{REVISION*:}}

The magic words REVISIONID, REVISIONUSER and REVISIONTIMESTAMP (with
friends) now exists as parser function to fetch revision information
from another page specified as param to the parser function.

Invalid title or non-existing title will return an empty string.
Requesting revision deleted information will always return an empty
string, because this is for public audience and goes into the parser
cache.

The parser function will register a template link to get updated with
refresh jobs on edit of the remote page. This is the same way, than
the parser function pagesize is working.

When the given param is equal to the current title of the parser, the
parser function will yield the previous versions on preview and on
substitution, that includes empty strings when used on page creation,
but using the values from the current version for page view, including
viewing old revisions.

Bug: 6092
Change-Id: Ib15a4e54c65192ec3caef71fd5dcb93fb6fc444e
Merge "Add expensive parser functions {{REVISION*:}}"