LP#1522638 egProgressDialog features and docs

LP#1522638 egProgressDialog features and docs

Use an HTML5 <progress/> element as the progress bar instead of the
Bootstrap progress CSS class.  The HTML5 element provides a more
accurate display.

Add support for 3 modes of operation:

* determinate - shows dialog and percentage progress
* semi-determinate - shows a value-less <progress/> but also displays
  the current value to indicate work happening.
* indeterminate - shows a value-less <progress/> with no specificat
  indication of forward momentum.

Adds a bunch of docs.

Rename egProgressModal to egProgressDialog for consistency with other
eg*Dialog's (which are also modal).

Signed-off-by: Bill Erickson <berickxx@gmail.com>
Signed-off-by: Terran McCanna <tmccanna@georgialibraries.org>