Update OPC DA

[kumajaya]

• Don't do any unnecessary preventions for string conversion problems
• Remove items and groups depend on FB config
• Code refactoring from char* to std::string
• Proper memory usage and deallocation

[kumajaya]

@azoitl @MartinMelikMerkumians
I hope my understanding to const std::string& is correct:

• No copy.
• No allocation in the heap.
• Quick behavior.
• Inform developers that the variable is not altered.

Reference: https://grapeprogrammer.com/const_string_reference_cpp/

[azoitl]

@azoitl @MartinMelikMerkumians I hope my understanding to const std::string& is correct:

* No copy.

* No allocation in the heap.

* Quick behavior.

* Inform developers that the variable is not altered.

Reference: https://grapeprogrammer.com/const_string_reference_cpp/

Yes this is my understanding of const references to std::string.

There is an exception to this rule: When C++ compiler could apply the move semantics to transfer the string's content into a newly created object then a pass by value is more efficient. Am I right @MartinMelikMerkumians ?