Allow Classes for type declarations inside documentation

Grape requires types to be specified using Classes, not strings.  This was problematic when using Entity.documentation to specify params restrictions while also exposing the entity as a Model to grape-swagger.

               module Entities
                 class Game < Grape::Entity
                    expose :level_name, documentation: { type: String }
                 end
               end
   

              #in a grape endpoint
               params do
                 requires :all, using: Entities::Game.documentation
               end
                
          
              
Without this patch the above code causes grape-swagger to consider String distinct from 'string' when type checking for swagger output on Models.  This breaks the swagger UI with "this.dataType.toLowerCase is not a function swagger"