Adds :kind and :kind! commands to Eval Plugin

[konn]

This pull request implements :kind and :kind! commands ala GHCi to Eval plugin.
The former displays the kind of a given type and the latter also displays the normalised form of a given type.

Examples

-- >>> type N = 1
-- >>> type M = 40
-- >>> :kind N + M + 1

evaluates to:

-- >>> type N = 1
-- >>> type M = 40
-- >>> :kind N + M + 1
-- N + M + 1 :: Nat

And

-- >>> type N = 1
-- >>> type M = 40
-- >>> :kind! N + M + 1

evaluates to:

-- >>> type N = 1
-- >>> type M = 40
-- >>> :kind! N + M + 1
-- N + M + 1 :: Nat
-- = 42

[Ailrun]

Thank you for the contribution!

[Ailrun]

Could you let me know why have you changed this test? It seems irrelevant to me.

[konn]

Yes, that change is not directly related to my change; but without this hack, at least on my laptop, Applies file LANGUAGE extensions test case fails due to the interference with import lens.
This issue seems already existent in the master branch and I wanted to avoid such errors to make my pull-request get merged as soon as possible. Indeed, I once wondered if I should make this change in this pull-request but I decided to include it since it's a minor change and somewhat related to Eval plugin.

But, yes, this change is semantically separate from this pull-request. Should I file this workaround as another pull-request?

[Ailrun]

I think it is worthwhile to post that as an issue, but for the separated PR, it's OK to stay this change as-is.

[Ailrun]

LGTM :)

[pepeiborra]

Looks good, nice!

[konn]

What does block this to be merged?

[konn]

Thanks!