Performance boost on adding rows from data refresh

- Accessing the API of DataTables properly via `.api()` method as documented on website
- No longer calling `fnAddData()`, adding rows to an array and then executing `api().rows.add(rows)` followed with a chain call of `draw()`. This results in a MAJOR performance boost in regards to refreshing the display and is the recommended way of doing so as stated in the documentation of jquery data tables