We would like Kotlin build scripts to behave as if all the `Action<T>`
parameters in the Gradle API had been declared as `T.() -> Unit` to
avoid the need for explicitly qualifying the single argument to the
given lambda expressions with `it`.

In other words, we would like users to be writing code like:

    copySpec {
       from("src")
       into("out")
    }

Instead of:

    copySpec {
        it.from("src")
        it.into("out")
    }

Where `copySpec` is declared in the Gradle Java API as:

    CopySpec copySpec(Action<? super CopySpec> configuration)

So far we have been able to avoid the qualifying `it` in some situations
via mindful use of inheritance and Kotlin extensions but a comprehensive
solution was still lacking. The underlying issue is that while Kotlin
does provide a type extension mechanism, type members still take
precedence over extensions and currently there's no mechanism to
instruct Kotlin otherwise.

In the future we might be able to implement a different solution to this
particular issue via a new Kotlin language feature still in discussion:

 -  https://youtrack.jetbrains.com/issue/KT-12848

In the meantime, by giving the Kotlin compiler a carefully crafted API
jar with all members that could potentially conflict with our provided
extensions removed we can work around the fact that interface members
take precedence over extension members and expose all the extensions we
want.

And that is the solution implemented in this commit:

  - Remove all API methods that take a last `Action<T>` parameter
  - Generate shim extensions that take a last `T.() -> Unit`

Proper treatment for generic types will be implemented in a future
commit.

Resolves: #52
See also: #54, #117