Add semantic versioning comments

Just trying to elucidate where we need to address versioning problems
Adds command to migrate v1 service instances to v2

[#63080352]
Add inline-relations-depth to service_plans query in CLI.

- This is needed to make sure that the necessary data about the service plans and their associated
services is returned to the CLI.
- [#63080352]
Improve messaging for migrate-service-instances

 - Add the warning message
 - Include the number of instances that will be migrated in the prompt
 - Refactor tests
 - [#63080352]
Use /v2/services with a filter to find plans

- Remove ServiceRepository.FindServicePlanToMigrateByDescription
- Add the more generic ServiceRepository.FindServicePlanByDescription
- [#63080352]
Return number of instances changed when migrating [#63080352]
Improved text readability [#63080352]
Merge pull request #82 from cloudfoundry/migrate-service-instances

Add migrate-service-instances command

[Finishes #65688722]