Make it easier to switch between hosts (and accounts)

[avborup]

Currently, if you want to submit to itu.kattis.com instead of open.kattis.com, you need to manually edit the .kattisrc.

I suggest adding an optional profiles section to kitty.yml where you can define multiple .kattisrc files and names for them (or just avoid configuration and have multiple files like .kattisrc, .kattisrc.itu, etc). Kitty would then be extended with a new use command, so you can easily switch between accounts like kitty use itu. This also allows users to use multple accounts on the same host.

This would require some file in which kitty can save state.