Delete _assets/NoteSkins/common/_Editor directory

82MB of psd files we don't really need to distribute, also the contents of the readme here are really weird.

_assets/NoteSkins/common/_Editor/_README BEFORE OPENING.txt

@@ -1,11 +0,0 @@
-These are the original PSD Photoshop CS5 files for the Editor noteskin.
-Normaly I dont make Readme's but for this one I make an exception for a reason.
-The Center Tap Note, Down Tap Note, and DownLeft Tap Note, are GIANT files.
-Which results in them taking up a load of mem when opened.
-I have a Q6600 cpu, and 8gig memory, And it even lags for me.
-So if you do open them please watch out because they will take a load of your cpu and memory.
-
-Also I'm putting these files under http://creativecommons.org/licenses/by-nc/3.0/ .
-So I dont get that JEWISH DANCE GAME drama and others.
-
-Alexander Griffin - Jousway/Zettbou, Creator of noteskin.