Remove check for on() and addEventListener().

[tomfaltesek]

Removed the if/else that checked for the existence of the on() and addEventListener() methods.

This is the block that was removed:

if (page.Page.on || page.Page.addEventListener) {
    console.log("NativeScript-globalevents auto disabled; functionality appears to be already present!");
} else {
  // Extend the Page object with the new events...
  // This code was left unmodified.
}

This should fix NathanaelA#7.

[tomfaltesek]

This might be overly simplistic. I'm anxious about overriding the NS Page on() and addEventListener() methods. Although this currently works in my NS Angular project, I'm not sure it's a great long-term solution.