Scan for environments in configured search paths

[MLNW]

Currently, it is only possible to provide a file to the CLI instead of being provided with a list of available environments.

Related to #7

[MLNW]

The scanning is implemented but not yet fully integrated with the CLI. It must be decided upon how to integrate environments.

One possibility would be to add a dagos env list command to display them and allow providing them to dagos env deploy instead of a file. This option would be in contrast to how software components are currently handled.

Another option would be to list found environments when running dagos env deploy and allow deploying them with dagos env deploy <environment>.

A third option would be to have commands like dagos env <environment> info|deploy.

Generally, it must be decided on what kind of interactions should be possible for environments. Some possibilities below:

• deploy
• info?
• update?
• validate?
• remove?