RemoveOldManualUserPages: Document and enforce required options

Follows-up dbdcceb182da5.

Current fails with unhelpful:

> PHP Fatal error:
> Call to a member function getId() on a non-object
> in GlobalCssJs/removeOldManualUserPages.php on line 23

Change-Id: Idfe430088136dd2724005583df41617df5e1ffb8
(cherry picked from commit ebe90f241fd4153fe91c83a83d2da128ca75de6a)
Add option to ignore the revision limit

Change-Id: Icb34bbcb0c723fea4bf9b953d3a90a78c78b53f6
(cherry picked from commit 0226c676374fbda2214b9062666f61cb22615d20)