Allow Credentials configs to be saved separately and referenced in desktops.yaml

[danhale-git]

Desktop hosts will always be unique but credentials may not. Currently credentials must be provided per desktop config but this will result in repeated configurations which will be difficult to maintain. Create a separate credentials.yaml to store credentials and add a new Credentials which references the entries in credentials.yaml.

Use this as an opportunity to consider renaming config files to .config and placing them in a .runrdp directory.

[danhale-git]

#13