Implement globbing operator for filters

The operators “=*” and “!*” do globbing in filters, e.g.:

$ gnt-instance list --no-headers -o name 'name =* "*.site"'
inst1.site.example.com

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>