Added .gitignore file.
Imported and transcribed existing code for the virtual machine.
Imported existing code and code examples for the compiler.
Moved class stack to own python package.
Moved language structures to own file.
Added simpliefied tree node class to Collection.
Implemented unverifying algorithmn to parse arithmetic postfix syntax into infix syntax tree.
Added toString method to TreeNode class.
Added toString method to class Structure.
Changed textual representation for debugging purposes.