Fix empty groups, add launch template support and show potential cost savings in the report

[timothy-cloudopsguy]

Let me know your thoughts. The Launch Template addition is a little more chatty in boto3, due to the extra call you must make to get the actual launch template version. The original pull only retrieves $Latest or $Default to the version which is unhelpful as I believe we need the integer value for the version.

I didn't try to make it neat in terms of a fancy one-liner here, because it got more complex than the original Launch Configuration.

I ran it in my current production and was able to recover ~$1,900/mo in savings. YMMV.

AMIs to be removed:
+--------------------+------------+-----------------------+--------------+
|     Group name     | candidates | EBS Storage recovered | Cost Savings |
+--------------------+------------+-----------------------+--------------+
| no-tags (excluded) |    256     |         19419         |  $1941.9/mo  |
+--------------------+------------+-----------------------+--------------+