Updated todo
Removed power operator.
Better matching of decimals.
Updated parser test.
Statements iterations moved to visitor.
WIP Implemented type structure - TypeChecker now broken!
WIP Made visitors return generic type - typechecker still broken!
WIP Removed DataType enum and TypeInitializer - TypeChecker still broken!
Fixed TypeChecker!
Renamed Context to Environment
Refactored INodeVisitor from interface to abstract class
Put Environment inside visitor to prevent argument bloat
Created Error object for error reporting
Improved IF-THEN-ELSE structure and more semantics in its parts.
Return Error type on failure.
Updated todo.
Merge branch 'master' into martyn82