Add CircleCI support

[idanshahar]

To support CircleCI, the following should be implemented:

1. Detect a CircleCI Yaml file in the repo. (regardless the SCM type - Local/GitHub/GitLab)
2. As part of the Fetch command: CircleCI files should be fetched as well
3. As part of the local validation, the validation should support CIrcleCI files as well
4. Review the exiting rules and Update/create new rules to support CircleCI. Some of the existing rules are relevant for any CI/CD and some are more CI/CD specific

[dimabru]

@idanshahar I think we need to enhance the description a bit here. The cli has grown and changed since this issue was created

[idanshahar]

@dimabru - I made some changes to the description. Feel free to add more technical details as you feel necessary.