add support to fetch xlsx reports

[keyn4]

Description of change

Add support to fetch xlsx reports

Config flags to enable:

    "list_reports": true,
    "discover_report_fields": true,

xlsx reports available from version "43.0":

"api_version": "43.0"

Accepts custom reportMetadata to sort and filter reports, via config file.
example:

    "report_metadata": [
        {
            "Sales_October_Report": {
                "reportMetadata": {
                    "reportFilters": [
                        {
                            "column": "Product.Name",
                            "operator": "greaterThan",
                            "value": "1 1/4 ADAPTER"
                        }
                    ],
                    "sortBy": [
                        {
                            "sortColumn": "Product.Name",
                            "sortOrder": "Asc"
                        }
                    ]
                }
            }
        }
    ]

Notes:
Report Name should be the DeveloperName and the fields name for sorting and filtering should be the entityColumnName not the label shown in the report.