Add ObjC generics to collections in PFQuery public header.
Add ObjC generics to collections in PFQuery public header.

Jericho25/Parse-SDK-iOS-OSX,dvanwinkle/Parse-SDK-iOS-OSX,MetaStackers/Parse-SDK-iOS-OSX,podkovyrin/Parse-SDK-iOS-OSX,manuyavuz/Parse-SDK-iOS-OSX,MetaStackers/Parse-SDK-iOS-OSX,gonzalonunez/Parse-SDK-iOS-OSX,manuyavuz/Parse-SDK-iOS-OSX,Jericho25/Parse-SDK-iOS-OSX,Jericho25/Parse-SDK-iOS-OSX,ParsePlatform/Parse-SDK-iOS-OSX,MetaStackers/Parse-SDK-iOS-OSX,natanrolnik/Parse-SDK-iOS-OSX,manuyavuz/Parse-SDK-iOS-OSX,JeckoHeroOrg/Parse-SDK-iOS-OSX,natanrolnik/Parse-SDK-iOS-OSX,JeckoHeroOrg/Parse-SDK-iOS-OSX,gonzalonunez/Parse-SDK-iOS-OSX,ParsePlatform/Parse-SDK-iOS-OSX,podkovyrin/Parse-SDK-iOS-OSX,JeckoHeroOrg/Parse-SDK-iOS-OSX,dvanwinkle/Parse-SDK-iOS-OSX