run-tests: added '--json' functionality to store test result in json file This patch added a new functionality '--json'. While testing, if '--json' is enabled then test result data gets stored in newly created "report.json" file in the following format. testreport ={ "test-success.t": { "result": "success", "time": "2.041" } "test-failure.t": { "result": "failure", "time": "4.430" } "test-skip.t": { "result": "skip" "time": "3.754" } } Otherwise, if '--json' is enabled but json module was not installed then it will raise an error "json module not installed". This "report.json" file will further accessed by html/javascript file for graph usage.