Merge pull request #343 from jeff1evesque/js_ajax_data

#341: Adjust 'ajax_data.js' to JSON datatype on 'success'
#342: load_dataset.php, remove 'print_r()' statement
Merge pull request #344 from jeff1evesque/php_load_dataset

#342: load_dataset.php, remove 'print_r()' statement
#342: load_dataset.php, add 'Python returns JSON object' case
#342: load_dataset.php, remove extra semicolon
#342: load_dataset.php, add 'print json_encode(arr_results)'
#342: load_dataset.php, move 'print()' inside 'if'
Merge pull request #345 from jeff1evesque/php_load_dataset

#342: Return JSON from 'load_dataset.php'
#346: ajax_data.js, remove unnecessary 'console.log()'