Added instance_profile_name parameter to ec2_lc module

This is a very simple change that exposes the "instance_profile_name" boto option when creating launch configurations (equivalent to the same option in the ec2 module).

Note that any IAM "role" created in the AWS management console automatically has a similarly-named instance profile created for it, so IAM roles  created that way can be applied directly to launch configurations, allowing the instances created with those launch configs to perform privileged AWS actions (e.g. downloading credentials from an S3 bucket during bootstrapping).