Move default options into config module

This starts making hc2002 usable outside hc2000, as an imported library.
Add command to "undo" role creation

This will detach instance_profile and role, remove policies from the
role and end by deleting both role and instance-profile.
Fix error message for prefix validation, allow tuple values
Let's not hide the scope list

The abstraction was already broken in one_of. It's not needed.
Have validate_keys take a validator

This enables more validation than just group membership and will be used
to validate _resolvable_prefixes in instance definitions.

With the onset of generalized key validations, error messages generated
during this step make it explicit a "key error" was found, with the
error prefix introduced here.
Add scope to manifest-related error messages

An initial_scope parameter is added to the generic validate function and
Context constructor.

Scope string is now tracked when validating manifests, including
user-data entry and file name if relevant. The scope may not be the user
scope, as the entries in the 'manifest' key will be injected to
'user-data' where validation actually happens.

validate function extracted so it can be reused in instance validation.
Soon!
Add separate validator for RunInstance mapping
whitespace
Rename loadbalancer => load_balancer
Hide EC2 and AutoScaling connections in modules
Re-enable spot instance requests

They were accidentally disabled when some temporary debug output made it
into 7c10fd94.
Expand RunInstance validation to cover our "instance" concept

An instance in hc2000 is supported by RunInstance, SpotInstances and
LaunchConfigurations and AutoScalingGroups. The point is to make the
transition seamless so it's important that they share a single
validator, even if it sort of has branches.
Move translate to translation module, drop key validation there
Propagate filenames, when known, to CloudInit

This is particularly useful when using CloudInit's integration with
Upstart.
Use python from environment, instead of hardcoding /usr/bin/python
Proof of concept image creation with hc2000

This goes to show what can be done with hc2000 and a little bit of
python. The example does not completely clean up after itself, as it
leaves the image-creation upstart job behind, but it does avoid infinite
loops and terminates the instance once it's done.