#Shunting-yard with support of unary operations

This project provides a way to evaluate mathematical formulas.
It is realised by an implementation of the Shunting-yard algorithm (Wiki article), it converts the infix formula to
postfix notation (or RPN - Reverse Polish notation) and by evaluating the postfix 'formula'.

The implementation of the Shunting-yard algorithm is slightly adjusted (compared to the Wiki article):

- support of unary operations like '-1' or '1+(-2)' added
- support of functions like sqr(9) removed.

This implementation supports the following:

Operations:
- '-' (subtraction)
- '+' (addition)
- '*' (multiplication)
- '/' (division)
- '^' (to the power of)
- '-1' or '+1' (negative/positive unary operation)

Number formats:
- integers
- decimals

The support of unary operations is realised by replacing the 'additional' plus or minus signs with a 'p' or 'm' in the postfix notation, handling them right associativ with high priority and calculating them differently during postfix evaluation.