Add inventory option to plugin

[bb-Ricardo]

This PR will add an "--inventory" option to be able to retrieve all system components in json formatted dictionary

The basic structure looks like this:

{
    "inventory": {
        "chassis": [],
        "fans": [],
        "firmware": [],
        "logical_drives": [],
        "managers": [],
        "memories": [],
        "meta": {
            "WARNING": "THIS is a alpha version of this implementation and possible changes might occur without notice",
            "data_retrieval_issues": [],
            "duration_of_data_colection_in_seconds": 0.018014,
            "host_that_collected_inventory": "hostname",
            "inventory_layout_version": "0.1",
            "script_version": "0.0.11",
            "start_of_data_collection": "2020-02-26T07:59:39+01:00"
        },
        "nics": [],
        "physical_drives": [],
        "power_supplies": [],
        "processors": [],
        "storage_controllers": [],
        "storage_enclosures": [],
        "systems": [],
        "temperatures": []
    }
}

THIS is the first alpha version of this implementation and possible changes might occur without notice

Fixes: #6