Replace "getQueryParams()" callsites in Phabricator

Summary: See D20136. This method is sort of inherently bad because it is destructive for some inputs (x=1&x=2) and had "PHP-flavored" behavior for other inputs (x[]=1&x[]=2). Move to explicit ...AsMap and ...AsPairList methods.

Test Plan: Bit of an adventure, see inlines in a minute.

Reviewers: amckinley

Reviewed By: amckinley

Differential Revision: https://secure.phabricator.com/D20141