Reporter::loadExternalConfiguration with json file

[anshooarora]

Each reporter must now have the capability to apply external configuration using JSON files. Version 4 and earlier had the ability to consume XML files, which will be deprecated starting v5.0.

[anshooarora]

This request is now complete, to load configuration, use:

final File CONF = new File("config/spark-config.json");
ExtentSparkReporter spark = new ExtentSparkReporter("target/spark/spark.html");
spark.loadConfig(CONF);

Format of the configuration json (this can change for each reporter):

{
    "theme": "standard",
    "encoding": "utf-8",
    "protocol": "HTTPS",
    "timelineEnabled": false,
    "offlineMode": true,
    "documentTitle": "ExtentReports",
    "reportName": "ExtentReports",
    "timeStampFormat": "MMM dd, yyyy HH:mm:ss a",
    "theme": "STANDARD",
    "js": "",
    "css": ""
}