add a tooltip to the "Deterministic Mode" checkbox
rename wml attribute deterministic_mode to random_mode
fix "from_side"

"from_side" is an attribute whose only purpose is to enable a check by
the server that a package is really sended by the side given in
"from_side", if thats not the case, the server sets an attribute
"side_invalid". The main purpose of this contruct is to disallow
cheating in mp.

this commit fixes a typo where i accidenelty wrote "side_from" instead.
And it also implements the option to have from_side=server (for random
seeds) .