Revert "Remove Resource::get method"

This reverts commit 1cce902a76b8b2b01b820079cff1abcf7f9793ed.
Remove $layout property and nicer overridable render

Also use absolute url in Location.
Removing the layout property impact performance a tiny bit but it makes
it possible to use layout with Http\Error, plus render output could be
cached anyway if that's an issue.