This commit aims to make it impossible to modify a 'Route' structure in
a way that violates expectations of a code-generated 'Route'. It removes
'Route::set_uri()' in favor of 'Route::map_base()', which allows for
safe modifications of the route's base.
In a similar vain, this commit also includes the following changes:
* 'Route::path()' was added to safely retrieve the route's 'path'.
* The base of a 'Route' is underlined during launch printing.
* 'Origin::into_normalized()' replaces 'Origin::to_normalized()'.
Fixes#1262.
Sergio Benitez