multiplayer!!

various bugfixes and such.
also bookmarks, temp song loaderm and undo overhaul with near complete multiplayer, but menu items disabled. i really wish i could split this into multiple commits, but i don't know how to work unreal.

(woops forgot to add one thing to the manual)

uh stuff. i'm putting it in the readme.

manual added for error checker
typo on delete button
tooltips shifted to the right for stats panel
total progress timer updates on load.
error count popup added
F added
dots are no longer completely ignored in double same direction checker
red note icon fixed

いきますよ！