Http Server: Support wildcard when searching for filename

This adds support for wildcard search in dirctory listing.

Both * and ? are supported, the match uses regular expression, where *
replaced by .* and ? replaced by .?.

A test for the wildcard was added.

Signed-off-by: Amnon Heiman <amnon@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>