Feature Request: MockedConstruction needs a setInitializer method

[joegottman1]

While it is possible to set a MockedConstruction's behavior at creation by passing an Initializer parameter as the second parameter to
mockConstruction method, it is not possible to set the Initializer after creation. This is annoying for several reasons:

1. It doesn't work well with annotating the MockedConstruction with @mock
2. It doesn't work with the common coding pattern of setting the default behavior of a mock in the setup() method and overriding it if necessary in individual tests.
3. It makes it impossible to set up a MockedConstruction so that the second mocked T created has different behavior than the first.

Since a MockedConstructor must contain an Initializer for the static function to work, it should be possible to add a method to set this after construction.