Add first nodes to syntax module
Add test for simple expressions
Add final spec for constant and primitive expression nodes. Add invoke expression
Add named expression node
Add values for boolean and string constant. Add tests for constant expresion nodes
Add tests for boolean and string constant
Add mutable node
Add tests for mutable nodes
Add rules for GNU C++ compiler
Add included headers as core source to cmake build script
Add ctor/dtor to ASTTree
Add type nodes and test for them. Draft for function and argument node
Add types to function and argument node
Add statements nodes and test for them
Add empty scanner and parser in syntax
Add rules to parser for parse function, statements and expressions
Add rules for scanner to parse keywords and constants
Changes in parser grammar
Fix cmake build script
Fix sienna executable