Fix /division arg not being valid and division image filename format

[lL1l1]

Issue

#6160 broke #4263 because it wanted to add a space to display the division better in text format in the score board, but the original #4263 was meant for the file names, for example goldIV_medium.png.

The /division arg was also not valid.

Description of the proposed changes

• Change the file name format to match the displayed text format.
• Fix the typo making /division and invalid command line arg.
• Assign divisions correctly in the launch script.

Testing done on the proposed changes

Launched a few games with the script and tested to see if the mod "4z0t's ScoreBoard" showed divisions properly when the "Show divisions instead of rating" setting was enabled. Made sure to check that grandmaster and unlisted worked with the mod as well.
The division arg format seems to match what is expected to be sent by the client and indirectly the server.

Checklist

• Changes are annotated, including comments where useful
• Changes are documented in the changelog for the next game version