Replace required "tool_id" for "community_ids" in the Implementations field for the Metrics Schema

[vsundesha]

"implementations": {
            "title": "The different implementations of this metrics",
            "type": "array",
            "items": {
                "type": "object",
                "properties": {
                    "tool_id": {
                        "title": "The tool id of an implementation of this metric",
                        "type": "string",
                        "foreign_keys": [
                            {
                                "schema_id": "Tool",
                                "members": [ "." ]
                            }
                        ],
                        "minLength": 1
                    },
                    "community_ids": {
                        "title": "The communities where this implementation is used",
                        "type": "array",
                        "minLength": 1,
                        "items": {
                            "type": "string",
                            "foreign_keys": [
                                {
                                    "schema_id": "Community",
                                    "members": [ "." ]
                                }
                            ],
                            "minLength": 1
                        }
                    }
                },
                "required": [ "tool_id" ]
            }
},

If a Metric is added and has the field "Implementation", a community should be required because, if we have a generic metric it would be related to at least one or more community/ies but not necessarily to one or more tools

[jmfernandez]

Fixed this and another issue on d63fd71d1c8150b074b0d91424bf13a8a395c13d