More convenient API for setting mocks

[ryanwersal]

Currently the pattern is:

var myMock = new Mock<IMyInterface>();
myMock.Setup(...).Etc();
Locator.CurrentMutable.RegisterConstant(myMock.Object, typeof(IMyInterface));

and it would be so much more convenient to remove the Splat calls and streamline getting these setup:

var myMock = autoMockContext.RegisterConstant<IMyInterface>();
myMock.Setup(...).Etc();

Additionally it might be ideal to use a callback to configure the mock?

var myMock = autoMockContext.RegisterConstant<IMyInterface>(mock =>
{
    mock.Setup(...).Etc();
});