Need to describe in the spec what is required for array storage, index an substrings (and create conformance units for the different optional items)

Some items to note:

• Not all historian are required to be able to store arrays
• If they do store array, they might not be able to process responses that retrieve index from the array (retrieve might be entire array only)
• If a historian stores strings, the same rule applies - they might not be able to retrieve sub strings only the entire string