Few small tweaks to the connection screen

Switched the checking files cl_mode to show a progress bar just like loading. I've seen a few folks in #tech-support think the game wasn't doing anything at this stage for servers with lots of files, probably due to having slow disks. This should communicate that waiting works.

Changed the confirmation prompt use MB if >=10MB instead of >=100MB Changed the overall progress bar to use MB if >=10MB instead of >=100MB More folks are familiar with MB than KB, and 5 digit KB numbers are kinda ugly imo