Spirit Board Improvements

[FoamyGuy]

A few more improvements based on feedback from JP.

• Included the spirit_messages.txt file in the project so the user can modify an existing file instead of having to create it. This should make it also appear on the drive structure screenshots as well I believe.
• Handle uppercase characters in the message by moving everything to lowercase before looking up the location in the dictionary map (which has all lowercase keys)
• More gracefully handle invalid characters that aren't on the spirit board. Previously the code would raise an exception when it attempts to lookup the character in the locations dictionary. Now it will print out a message in the serial output and skip the invalid character moving on to the next character in the message.