Added automatic API key switching

Will switch the API key used for the custom search to the next available
key when the current key has reached its maximum number of queries

If no available key is found the program will exit
Improved daily queries exceeded detection

Explicitly checks for "returned \"Daily Limit Exceeded\"" in the
HttpError
improve console output

Made the output to the console more user friendly and descriptive
Removed duplicates, API keys, search engine keys etc
Merge branch feature/Multiple-Api-Keys into 'Master'