TypeScript: improve UseCase#execute typing

From https://github.com/almin/almin/pull/101#discussion_r103071022

Currently, Following pattern is pass.
We want to improve this.

```ts
class UseCase extends UseCase {
    execute(value: string) {
        // do some
    }
}
const useCase = new UseCase();
// FIXME: This execute(number) is pass!
context.useCase(useCase).execute(42).then(() => {
  
})
```