(bug 26548) Make multi-paged documents (PDFs) work with ForeignAPIRepo (aka InstantCo...

(bug 26548) Make multi-paged documents (PDFs) work with ForeignAPIRepo (aka InstantCommons).

This adds a new parameter to the query=imageinfo (and query=stashimageinfo) that takes rendering
parameters other than width and height. This could be page for pdf's and DjVu, or thumbtime for ogg's, etc.
Syntax is &iiurlparam=param1=value1|param2=value2|... I'm not sure if that really fits with the normal way
of doing things in the api, but couldn't think of anything better since the parameters are arbitrary.

I also noticed that some of the pre-existing error codes in query=imageinfo seem to duplicate the module prefix. I'm
not sure what the deal with that is, but i did not follow that example in the new error codes i introduced.

Note: In order for this to work, both the foreign repo and the local wiki have to be running this code.