changes in repairFiles commenting and new functions included

comments made better for: repairFiles(),
repairFolder(),writeToSearchLogs()
new function: saveUsage() to store time details of each time app is used
new functions and exception handeling in previous functions implemented

added a call to function to save usage data to files -> saveUsage()
exceptions.log file added to save exception of records of user and to be
later uploaded to server
exception handeling added to writeToSearchLogs() and saveUsage()
function saveException() added to save identified exception to files
and
throwNonRecoverableError() function to handle unidentified exceptions
and throw a messageBox to show exception to user