Adding ability to execute stryker only for the changes and in parallel for faster execution

[manikandanid]

Have made changes to include following capability

1. For a given commitId, get the project pair (functional project & test project) in which changes are done. if no commit id is available, then entire project pair in the solution will be considered for execution
2. Run stryker in paralllel using start-job cmdlet and track for the completion
3. Combine json report had issue for latest stryker version and fixed