strcheck errors for string arrays

[sco1]

The strcheck helper method is currently hardcoded to error out when presented with an input that is not of type char or cell:

if ~iscell(newString)
    msgID = sprintf('legtools:%s:InvalidLegendString', src);
    error(msgID, ...
          'Invalid Data Type Passed: %s\n\nData must be of type(s): %s, %s', ...
          class(newString), class({}), class('') ...
          );
end

With the addition of the string data type in MATLAB R2016b there is another valid option for representing arrays of strings that is currently not supported by legtools

[sco1]

A fix has been implemented and will be tested in the morning when I finally get around to installing R2016b on my development machine.