Major improvements:
- For EC2, changing the paradigm for how permanent resources (e.g. the EC2Alloc dynamodb table) are created. meadowrun-manage-ec2 install now sets up all permanent resources, and we set up a meadowrunUserGroup that has just enough permissions to run meadowrun jobs but not enough to set up the permanent resources. On first run, instead of setting up permanent resources that don't exist, throw a helpful error message indicating that the install command needs to be run first