Added Lots of Documentation

Added some nice to haves
Improved and Unified General Code Layout

MathKit/MPExpressionTokenizer.m

@@ -52,7 +52,7 @@
                             @"((?:\\d+%@(?!\\d+))|(?:(?:\\d*%@){2,}\\d*)|%@(?!\\d+))|" // Substitute with decimal separator 3 times
                             @"((?:\\d+(?:%@\\d+)?)|(?:%@\\d+))|" // Substitute with decimal separator 2 times
                             @"(sin|cos|tan|asin|arcsin|acos|arccos|atan|arctan|lg|log|ln)|"
-                            @"([A-Za-z])|"
+                            @"([A-Za-zπ])|"
                             @"(!)|"
                             @"(=)|"
                             @"(\\s+)"