Deferring system dependency usage

[sdelliot]

Installing and using FIREWHEEL without all dependencies installed (e.g., minimega, discovery, and the running GRPC server) is currently infeasible. However, in many cases, users will find it useful to have a "bare-bones" install that does not need to launch VMs or perform actions of these external services. In particular, laptop or container-based development environments would be valuable to develop experiments and perform some testing on topology and VMR schedule correctness without invoking these services. Fundamentally, this will save the cost of performing simple development on large server infrastructure. This new feature proposes deferring the invocation of system services to as close to VM launch time as possible.

• Deferring the uploading of VM Resources. This defers the dependency on minimega as well the need for generating/storing large binaries/images on local development environment. See Deferring the uploading of VM Resources #33
• Deferring minimega API usage in the CLI. minimega is currently used to support SSH connections to VMs. However, the SSH-related classes are within the firewheel.cli.utils module. Creating a new module will defer the import/usage of minimega until needed.
• Enable the RepositoryDB to using a local file rather than relying on the GRPC server. This is the one component where the GRPC server provides no value but it's dependence hinders installing local MC repos without the service started and accessible.

As other items become apparent, they can be added to this list.