Add LIMIT clause to EyeQL documentation

We need to update http://confluence.atlassian.com/display/FISHEYE/4.+EyeQL+Reference+Guide with the new SQL-style LIMIT clause:

select revisions
(from (dir|directory) word)?
(where clauses)?
(order by date (asc | desc)? )?
Notes: asc produces 'ascending order'.
desc produces 'descending order'.
(group by (file|dir|directory|changeset))?
(return return-clauses)?

with:

(limit limit-args)?

added at the end after the return clause description.

We'll also have to add a description of limit-args down the bottom somewhere:

( duration | offset , duration | duration offset offset )
Notes: Limits the number of results to return. Offset specifies the starting point of the truncated result set and duration specifies it's length.