Follow up on #2303 and #2302.

This PR merges the two different response types for the type and completion command. We now provide all the AST information for both of these.

The format for the returned completions has thus changed from:

{ "module" : "Text"
, "identifier" : "Text"
, "type" : "Text"
}

to:

{ "module" : "Text"
, "identifier" : "Text"
, "type" : "Text"
, "expandedType" : "Text"
, "definedAt" : "Maybe SourceSpan"
, "documentation" : "Maybe Text"
}

The type field now contains the annotated type, if we found it by parsing the sourcefiles. If we didn't find any annotation it still contains the type with fully expanded type synonyms. This should provide a better default for the editors and if they still want to show the expanded types that is now available via the expandedType field.

The documentation field is always Nothing for now, but I intend to fill out that information soon, so I thought I'll change the API just once instead of twice.

Because all the old fields remain we shouldn't break any editor plugins, give better type information for the end users and allow for more features on the editor side through the new fields.

TODO:

• Document the new API
• Write a few tests
• Squash commits