Remoting and Web API : Add support for a Shared Secret to avoid the user of a username-password

[michaellwest]

Following the work I did here: https://github.com/michaellwest/westco-security (which is almost an exact copy of what @kamsar did in Unicorn).

Steps:

• Setup shared secret
• Call web api using shared secret rather than username/password.

[michaellwest]

Currently exceptions are thrown and then caught. Should something else be done instead?