[tools]Update stats.py to save the result in a csv file

Update the ref and bdd tests coverage
Update the Upstream test coverage
Output the result to coverage.csv
[wrt] Add subcase to manifest and packtertool suite
Merge pull request #1267 from wanghongjuan/wrt/update-tests.full.xml

[wrt] Add subcase to manifest and packtertool suite
Merge pull request #1250 from chenxix/tools/modify-coverage-script

[tools]Update stats.py to save the result in a csv file
improve tool with increment method
Merge pull request #1269 from cicili/change-ws-docroot

improve tool with increment method