Remove unnecessary utilities (#99)

- Comparable.clamp is already defined
- Boolean class does not exist
- String#start_with? already exists
- String#end_with? already exists
- String#bytesize already exists
- String#capitalize already exists
- Integer#digits already exists
- Array#first and Array#last already exist
- Array#shuffle already exists

Ruby's own Integer#digits returns an array with the least significant digit as the first array element. That means that the method's only usage has to be appended with a call to Array#reverse.

Data/Scripts/012_Battle/005_Battle scene/004_PokeBattle_SceneElements.rb

@@ -191,7 +191,8 @@ class PokemonDataBox < SpriteWrapper
   end
 
   def pbDrawNumber(number,btmp,startX,startY,align=0)
-    n = (number==-1) ? [10] : number.to_i.digits   # -1 means draw the / character
+    # -1 means draw the / character
+    n = (number == -1) ? [10] : number.to_i.digits.reverse
     charWidth  = @numbersBitmap.width/11
     charHeight = @numbersBitmap.height
     startX -= charWidth*n.length if align==1