made AST visitable, and added ASTVisitor class
added some generation functions
added genssavisitor
gradually adding implementation for AST nodes
added 'if' and 'while' SSA generation
added SSA for 'for' loop
added SSA for unary operators
added several functions
added checkvisitor
removed some memory leaks
removed some leaks again
refactored code
improved performance with use of move semantics
added some commands
added optimizer
almost works
separated TAC, Block, Arg and Command classes
refactored code, and added operator== to Arg and Command
fixed bug with optimizer
removed debug output in optimizer