Initial, incomplete. Have fun!
added a method that helps to decide if a type is already defined or not
astyle
Added a get_type method for expressions. The method is implemented for Unary- and PrimaryExpressions (some of them are not done yet). Binary- and PostfixExpressions only have the method but it's not implemented yet.
astyle
Merge branch 'typechecker' into dev

Conflicts:
	src/ast/Type.cpp
	src/semantic_analysis/SemanticAnalysis.cpp