Add new option `-resetSimulator`. Reset simulator if (un)installation fails.

New option tells xctool to reset iOS simulator content and settings and restart it before running every app test run.

Sometimes iOS simulator fails to install or uninstall test host app. If that happens we were retrying 3 times before failing, now we are additionally resetting simulator content and settings folder after each attempt.
Merge pull request #353 from facebook/nekto/clean_sim_folder

Add new option `-resetSimulator`. Reset simulator if (un)installation fails.