Fixes #998.

Change program type from ByteString to String and remove RankDir because
that can be configured in the input.

Remove duplicate module `IHaskellPrelude`.

remove module from `main`, and promote from `other-modules` to
`exported-modules` in `library`.

Fixes #971.

Implement update_display_data message

This commit adds new message update_dispaly_data and updates
display_data message to add optional transient field which
is in turn used by update_display_data

Fix protocol communication with jupyter-lab.

Moves package from using jupyter-notebook to the jupyter-lab.
Both backends can still be used using: ihaskell-notebook and
ihaskell-lab respectively.

The IPython specification for the metadata does not
define that all fields in metadata must be textual.
Latest Jupyters lab uses that feature so the parsing
mechanism became incomplatible with the protocol.
We change Metadata to be an Aeson.Object and introduce
a 'Metadata' newtype in order to keep that explicit
and open for the later changes if needed.

Fixes #912.

Hoogle v5 uses a different json representation for the data, requires a
new URL and also contains HTML markup inside the json fields.

This commit removes all markup to be able to handle the hoogle responses
using the same structure as with the previous response structure (from
hoogle v4).

This reverts commit 01366b63.

This reverts commit 31a59439.

Hoogle v5 `docs` field already contains markup, so we just use the field
content directly.