Added VibeCustomMain to all examples with an own main function.
Using the new download URL scheme for the DUB registry.

The url/downloadUrl fields in the package description from the registry are now deprecated an will be removed later.
To keep VPM running for a bit longer, this change makes it compatible with DUB in this regard.
Module structure changes:
    1) Added vibe.http.restutil module that contains HTTP/REST-agnostic meta-programming utilities
    2) Moved all matching function/templates from rest to restutil

Features:
    1) Implemented UDA support for REST interfaces - @method and @path

Rework;
    1) Adjusted formatting in vibe.http.rest to single most prevailing style
    2) Reworked all code generation functions to use token strings + format
    3) Replaced copy-paste with table lookup in extractHttpMethodAndName

.. and varios minor tweaks I have probably done subconsciously.