Access key and IAM identifiers updated - EUCA-5260 EUCA-5999 EUCA-6001

Access key identifiers now start with AKI and are 20 rather than 21
characters in length.

We now use the AWS prefixes for IAM identifiers:

  AID - user
  AGP - group
  AIP - instance profile
  ARO - role

EUCA-5260
EUCA-5999
EUCA-6001
Add context for IAM policy evaluation - EUCA-4247

IAM policy evaluation now supports use of a context that can cache
information for some client controlled scope. Describe / list actions
now use a context for the lifetime of a filtering predicate (so per
request)

The main request processing context is updated to cached the system
administrator flag, this information was being repeatedly loaded from
the database causing performance issues when filtering resource lists.

There are minor updates to the Auto Scaling and EC2 services to ensure
they use filters from RestrictedTypes effectively.

EUCA-4247
Update tests for storage changes.
Merge branch 'dev/sjones/EUCA-5999' into testing
Merge branch 'dev/sjones/EUCA-4247_34' into testing