configure.py: Make messaging not quite so specific to Amazon EC2

pem keys for example are not specific to Amazon. I am using one to
connect to an OpenStack VM for example.
configure.py: Prompt for user but default to "ec2-user"
src/example_01/access_machine.py: generalize so we can use a remote_user
other than "ec2-user" by reading it from ansible.cfg
src/example_02/auto_update_machine.py: generalize so we can use a remote_user
other than "ec2-user" by reading it from ansible.cfg
Fix small PEP8 / pylint violation
Clean input for configure.py
Regenerate output files
Merge pull request #63 from glenjarvis/refactor/generalize_so_not_quite_so_specific_to_ec2

Refactor/generalize so not quite so specific to ec2