Update documentation examples with assign_public_ip, instance_count

[kral2]

Hello,
The file examples/instance_default/terraform.tfvars.template and the example snippet in the file examples/instance_default/README.md are missing the initialization of the variables assign_public_ip, instance_count

Pre-existing problem and not in the scope of this PR. This should be a distinct issue.

Originally posted by @kral2 in #49 (comment)