Show source for tweakdefs and tweakunits instead of base64 in lobby

[Jordan-Cottle]

When joining a lobby with tweaks, it is hard to tell what the tweaks do. Not everyone can read lua or understand the tweaks from their source, but effectively noone can read base64 without decoding it.

There should be no reason the client has to display the base64 version, or even require players making tweaks to apply/paste in the base64 version even if the server that uses this data requires it in base64 format.

[p2004a]

Just FYI, This isn't on purpose, it's "PRs welcome" situation.