The SoftLayer provider should honor the authorizePublicKey option

Currently the SoftLayer ComputeService implementation ignores the TemplateOptions#authorizePublicKey option. The custom SoftLayerTemplateOptions provide a way to attach an existing ssh key to a node, but the generic options should be taken into account too.

The following lines configure the SSH keys when creating a node:
https://github.com/jclouds/jclouds/blob/master/providers/softlayer/src/main/java/org/jclouds/softlayer/compute/strategy/SoftLayerComputeServiceAdapter.java#L200-L207

If the authorizePublicKey option has been set, a new SSH key must be created and assigned to the virtual guest. This may require creating the missing API methods to manage the SSH keys.