Fix #1276 - Implement WebAPI action conventions and overloading

This change adds ApplicationModel conventions that can enable WebAPI
action conventions (verb mapping) and WebAPI overloading.

The conventions activate when a controller has a marker attribute.
ApiController has this attribute, so any ported code will automatically
opt-in.

Also ported some old tests for action selection to our new functional test
framework.
Why do you need the named version? For the case a user has 
```
{controller}/{action}
```