[Ide] Allow completion tooltip without signature

Not all tooltips for completion items necessarily *have* a signature.
[Ide] Fix completion item tooltips

If a CodeCompletionItem has a Description, put that in
the tooltip. This used to work but was broken by the
TooltipInformation changes.
[AspNet] Improve type resolution in aspx
[AspNet] Re-enable completion tests

The resolution fixed made them more robust.
[AspNet] Add tests for control property completion