Implement debug mode

Debug mode doesn't terminate the server when an error occurs, instead it
reports the error and sleeps indefinitely until it receives SIGINT at
which point the server wil be terminated. The intent is to allow the user to
access the server directly to figure out what went wrong while still ensuring
the server is terminated.
Vastly improve the bundling of required certs and keys

The ec2-ami-tools currently exclude all potentially sensitive files,
even ones that are widely available for tools like apt and which will
prevent the tool from running. This fixes this by scanning the
filesystem for any of these files to include before it actually
uploads anything sensitive. If you actually do have sensitive files
to exclude then you can specify them manually.
Output commands being executed to STDOUT
v1.2.0

 - Added the --debug flag
 - Default to including the various .crt, .pem and .gpg keys that are
   normally excluded by ec2-ami-tools
 - Output SSH commands we're executing by default