Add p5-Net-OAuth2: OAuth 2.0 implementation in Perl

OAuth version 2.0 is a follow-up on OAuth 1.0, which is not supported by
this module. The specification for version 2.0 can be found in

- RFC6749, Authorization framework: http://tools.ietf.org/html/rfc6749
- RFC6750, Bearer token usage: http://tools.ietf.org/html/rfc6750

Start with one these modules:

- Net::OAuth2::Profile::WebServer
- Net::OAuth2::Profile::Password

(schmonz)