Implement MariaDB specific %magic commands

implement MariaDB specific %magic commands

• eg. %bar %pie %line %df
  -(later: %stackedbar and %graph, which heuristically picks between bar/pie/line),
  thereby integrating with matplotlib by displaying the results of the last SELECT statement as a graph

• show the syntax of the matplotlib commands (and any heuristics interesting to the user, so the user can adjust the select, or request better heuristics from us)