Prefs: Remove preferences design

I think I can get by without this now ...

Signed-off-by: Anna Schumaker <schumaker.anna@gmail.com>

design/gui.txt

@@ -3,7 +3,7 @@
 		*
 
 == Depends ==
-idle file prefs
+idle file
 
 Gui: (ocarina/*)
 	The GUI will be written in C++ using gtkmm3 for (hopefully) cleaner code.

design/prefs.txt

@@ -1,22 +0,0 @@
-== Files ==
-	ocarina/include/
-		prefs.h
-	ocarina/lib/
-		prefs.cpp
-
-== Depends ==
-idle file
-
-Preferences: (lib/prefs.cpp)
-	Preferences make use of a special index where the set<int> is always
-	size 1.  Preferences will be in the prefs namespace.
-
-- Index:
-	Index prefs(prefs.idx);
-
-- API:
-	prefs :: set(string, val);
-		prefs.replace(string, val);
-
-	prefs :: get(string)
-		return prefs[string].begin()