Show time graph in local time

This PR is related to issue #140, Timezone is not adjustable for Time based axis.

My goal is somewhat more narrow than the popular asks in issue #140. I only attempt to enable chart to use user-agent default time format.

I forked a new file `Fixtures.LocalTime.js` based on the original `Fixtures.Time.js`.

The only change to original code is in `Axis.Time` allowing `timeFixtures` to be specified.

I updated extension.html examples to show usage.