[HRnet] Date picker is slow, sometimes unresponsive

[mja2128]

The date picker jQuery plugin that we use on the Create Employee page is often times slow and sometimes completely unresponsive. Let's convert this to a React component to optimize the rendering and hopefully speed up the overall app.

Here's the plugin we are currently using for date pickers: https://github.com/xdan/datetimepicker

These are the ones we are referring to:

Expanded: