Further improvements

[laser-shark]

• Calculator: Allow TokenStream to be initialized with strings: TokenStream TS("3 + 4")
• Calculator: Use the same Error object in both Parser and TokenStream - maybe convert Error to a proper class first and think about a return value so that Parser doesn't have to return 0 when an error occurs.
• Remove all cout statements
• Calculator: allow use of variables along with the memory: x = 5; x + 4 etc. Store and access variables in a map.
• Calculator: when displaying a result, show the memory slot it has been saved to: [m4] 15.5
• Calculator: rename Parser to Calculator and TokenStream to Parser
• Config: add GUI related variables to config (line-height, colors, ...)
• Add better point support for getIntersections() (It should take a Point as parameter and convert to a small circle to work as intended)
• Add intersection function for circle (isn't implemented yet)

[ColdIV]

The intersection function doesn't work for circles yet, this should be fixed.