#393: Add ability to clear solution explorer search before finding.

[joeburdick]

This solution works but has one potential drawback. Though the Solution Explorer will stop filtering items by the search query, the query string does not leave the search box. I could not find a way to make this box clear (and I am not even sure that is the behavior one would want.)

[codecadwallader]

Thanks for putting this together! I pushed some minor tweaks, including promoting when the IServiceProvider is initialized to resolve a unit test execution issue.

I think the text still being present is a little awkward, but since it's an opt-in feature it's something that can be improved upon. Merging in accordingly.

[codecadwallader]

The CI build with this change can be found here for testing: http://vsixgallery.com/extension/4c82e17d-927e-42d2-8460-b473ac7df316/