Model Redesign: Added Reference Frames

Added Inverse Functions
UI Redesign
Cleaned Code

MathPad/MPExpressionEvaluator.h

@@ -15,15 +15,9 @@
 
 @interface MPExpressionEvaluator : NSObject
 
-// Do not instanciate yourself, use evaluator property of MPExpression instead
 - (instancetype)initWithExpression:(MPExpression *)expression;
 @property (readonly, nonatomic, weak) MPExpression *expression;
 
-@property (nonatomic, strong) MPExpressionTokenizer *lexer;
-
-- (void)expressionDidChangeInRange:(NSRange)range
-                 replacementLength:(NSUInteger)replacementLength;
-
 #pragma mark Evaluating Expressions
 @property (readonly, nonatomic, copy) NSString *definedVariable;