Keyboard shortcuts in Mac should use the Cmd key instead of Ctrl

[r03ert0]

Keyboard shortcuts in Mac should use the Cmd key instead of Ctrl.
The keyboard shortcut assignment in the initMicrodraw function should check for 'Mac', probably like this:

if (navigator.userAgent.indexOf('Mac OS X') != -1) {
  $("body").addClass("mac");
} else {
  $("body").addClass("pc");
}

[r03ert0]

Commit 69215c9 handles mac and pc shortcuts. I changed the shortcut functions to take an object as first argument with mac and pc shortcuts such as {pc:"^ z",mac:"cmd z"} (the space is important!). The next argument is the function callback. To enter key codes directly, use "#46" for example. I also updated the code for the delete key in mac which is not "#46" but "#8".