Fix: JSON serialization/deserialization, cmd handling, admin request

[GaMeRaM]

• Corrected paths handling so now it correctly escapes strings that have spaces
• Fixed empty 'env' key handing in apps.json
• Fixed checks for existing games and games that launch using steam:// cmd
• Added request to launch as admin if needed
• Wait for button press before exiting to make reading logs possible

[JMTK]

Thanks for the fixes! I ended up having to just fully delete my apps array in my json file because of just some serialization issues, but that fully fixed it on my end.

I think possibly it would be better in the future to ignore "invalid" properties during deserialization rather than fully break but that's a separate issue. That way this app isn't contingent on the existing apps.json on being valid