Verify the CONTENTS of input files on startup (and handle bad files)

[RVRX]

To prevent any incorrect tampering by the user that might lead to the application crashing.
On that note, throwing exceptions when the file has bad data is important as well to stop crashes even if files are bad.

[RVRX]

This would involve:

teams.txt

• check for illegal chars
• make sure each line follows the "Name|ABBR" format
• Issue a warning if a team is missing an image
• No images with no team in the txt (warning)

maps.txt

• make sure each map in txt has an image

TimerLength.txt

• has a positive value
• nothing else

output/Timer.txt

• might need to make sure this exists, unsure how the program will behave if it doesn't