* ELECTRON-788: clean cache on bad exits
A few customers have reported that the cache gets corrupted when the app is not exited cleanly. And, upon the next start, we get cache_read_failures.
This fix adds an extra check during startup and exit to check if the app was exited cleanly and deletes the corrupted cache folder accordingly during startup.
* ELECTRON-788: add menu item, use electron session cache clear logic
Adds a new menu item to clear cache and reload the app.
Also remove the old logic of deleting the cache folder manually and use electron session api to clear the cache.
* ELECTRON-788: refactor code
