Validate data:image inputs for media commands
Validate data:image inputs for media commands

This gives explicit messages to ensure people don't try to /show it.

xfix/Pokemon-Showdown,svivian/Pokemon-Showdown,svivian/Pokemon-Showdown,xfix/Pokemon-Showdown,svivian/Pokemon-Showdown,xfix/Pokemon-Showdown,svivian/Pokemon-Showdown,xfix/Pokemon-Showdown,xfix/Pokemon-Showdown,svivian/Pokemon-Showdown