A few enhancements to the report html

[zhenyun]

• add "unit" to the sub-metric (needs to be in each metric)
• should we separate the metrics under ./resources? it could be a very long list of files. say, with sub-dir being the metric name under ./resources?
• currently under root dir, there are N+1 html files generated where N is the # of metrics. Should we move the N htmls to a separate directory?
• Create one entry to the report