Adding support for form parameters for PUT and PATCH method types

Adds support for form parameter type for PUT and PATCH methods.

Such as the name parameter in the example below.

```ruby
class FormParamApi < Grape::API
  format :json

  params do
    requires :name, type: String, desc: "name of item"
  end
  post '/items' do
    {}
  end

  params do
    requires :id, type: Integer, desc: "id of item"
    requires :name, type: String, desc: "name of item"
  end
  put '/items/:id' do
    {}
  end

  params do
    requires :id, type: Integer, desc: "id of item"
    requires :name, type: String, desc: "name of item"
  end
  patch '/items/:id' do
    {}
  end

  add_swagger_documentation
end
```