labextension npm dependency bounds loosen

Relax upper version bounds on the jupyterlab alpha dependencies
for ihaskell_labextension. It looks to me like these version bounds
were intended to allow the entire major alpha 0.*.* version range, but
the the prefix caret only includes minor versions if the major version
is 0.

Let's set the upper bound to 2.0.0, because according to SemVer, that
is the next version number which we would expect to have breaking
changes.

Attempt to set error status

Change extend to override in release.nix

Make unique labels using a timestamp for svg elements.

This reverts commit 96fe2ef5, reversing
changes made to e373bd3d.

Remove conversion of svg to html for generic usage.

ihaskell-widgets: Port to vinyl-0.9

Fixes #998.