Change return type of EmailCheckComponent

[dandanlen]

I think we should avoid using primitive types as the type argument for ExplorerComponent<>. The type arg should be something unique to the component.

For example, in this case there is another ExplorerComponent<bool> elsewhere in the code (EmailCheckComponent) - this will cause confusion when the dependency injector resolves class instances. (I suspect you might get strange results when you run this on a text column).

I would suggest defining a private Result or ExplorationMetadata class containing the Exploration info. We will add more items to this (I have a branch ready where we can insert the git commit hash and ref from the docker image).

Originally posted by @dandanlen in https://github.com/diffix/explorer/pull/175

[dandanlen]

See also this comment

We should add the class constraint the to the generic type parameter in ExplorerComponent.

[AndreiBozantan]

closed with #189