Fix array to string conversion error (issue #65)
This version introduces multiple enhancements:

checking that content given in generate is array, and convert it to string with log information

Details of additions/deletions below:
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Modified:   /BLUE_FRAMEWORK/packages/CORE/display_class.php
            -- Modified --
               generate method, added checking content by _checkContent method
            -- Added --
               _checkContent method to check content, convert it and create log file