CloudStackApi should extend Closeable

Without that, you can't actually do view.unwrapApi(CloudStackApi.class).
JCLOUDS-303. unwrap should permit subtypes
JCLOUDS-303. unhook ApiMetadata type hierarchy from ec2
[JCLOUDS-302] Remove unnecessary String construction in HttpUtils
JCLOUDS-305. Disable S3 virtual host buckets for generic S3

Not all S3-compatible providers support virtual host buckets and thus
we should disable this feature by default.  Continue to enable virtual
host buckets for AWS-S3 which supports this although this feature
suffers from DNS settling issues.  Ran ran integration tests against
AWS-S3 and Scality using its S3 API.