Implemented resolve method for LayerSymbol classes and started implementation of CoCo for parameter type check.

Still missing ShapeSymbol, DimensionSymbol, output shape calculation and method resolve method.

Started implementation of ArchValueSymbol and VariableSymbol.

Added method definitions.
Added math expressions.
Added serial and parallel argument sequences.

Changed ErrorCodes and error messages.
Added ASTGroupStructure methods.

Added keywords 'def', 'group' 'output' and 'repeat'.
Added more tests and architectures of existing networks.