Token: Rename the `value` entity to `identifier` one
StatementElement: Rename the `value` entity to `identifier`
TokenNull: Fix implementation of the Produce method
VariableTable: Implement the GetValue method
Include C++ standard headers instead C ones
Remove the Variant class
Move scripts for launching tests to the `testsuite` dir
OperatorMultiply: Implement the Reduce method
Operator: Fix bug with reducing nonexistent statement element
Initial add README.mkd file
Release 0.2