Implement ability to read parameter from yaml files

[ahelmbr]

Add ability to read all information from yaml file(s) - this could be a single parameter or a block of parameters or at least the whole command could be packed into a yaml file and read from there:

Identifier for reading from File is @<fileName> examples: mqtt con -u @myname.yaml mqtt @myFile.yaml

Content should look like described in the example:

mqtt: _version: 5 method: con client: identifier: C1 user: Max password: "$" cleanStart: 1 sessionExpiry: 0 will: properties: p: - "p1:x1" - "p2:x2" topic: "/myLastWill" message: "@/path2my/will.yaml"