This commit entirely rewrites Rocket's URI parsing routines and
overhauls the 'uri!' macro resolving all known issues and removing any
potential limitations for compile-time URI creation. This commit:
* Introduces a new 'Reference' URI variant for URI-references.
* Modifies 'Redirect' to accept 'TryFrom<Reference>'.
* Introduces a new 'Asterisk' URI variant for parity.
* Allows creation of any URI type from a string literal via 'uri!'.
* Enables dynamic/static prefixing/suffixing of route URIs in 'uri!'.
* Unifies 'Segments' and 'QuerySegments' into one generic 'Segments'.
* Consolidates URI formatting types/traits into a 'uri::fmt' module.
* Makes APIs more symmetric across URI types.
It also includes the following less-relevant changes:
* Implements 'FromParam' for a single-segment 'PathBuf'.
* Adds 'FileName::is_safe()'.
* No longer reparses upstream request URIs.
Resolves#842.
Resolves#853.
Resolves#998.
Sergio Benitez