JCLOUDS-303. unwrap should permit subtypes
JCLOUDS-303. unhook ApiMetadata type hierarchy from ec2
Fix EC2 live tests

This removes
org.jclouds.ec2.compute.functions.PasswordCredentialsFromWindowsInstanceLiveTest
due to there not being an easily detectable valid AMI for it to run,
and low interest in actually running it in the first place.
Fix aws-ec2 live tests

Involves some non-trivial reworking of EC2 security group
translation/binding, but it was necessary.

Still problems with a number of tests:
- org.jclouds.aws.ec2.compute.AWSEC2TemplateBuilderLiveTest#testTemplateBuilderWithLessRegions
- org.jclouds.ec2.compute.EC2TemplateBuilderLiveTest#testTemplateBuilderCanUseImageIdWithoutFetchingAllImages

Those seem to be failing because there's caching going on that they're
not expecting, but I could be wrong.

Also failing:
- org.jclouds.aws.ec2.features.PlacementGroupApiLiveTest in general
- org.jclouds.aws.ec2.features.SpotInstanceApiLiveTest - a couple tests