Refactor to use Revealing Module Pattern

Code completely refactored to conform to revealing module pattern:
-All variables and functions declared under adminView namespace to
avoid polluting global.
-New css and settings objects contain all configurable values for
centralized configuration.
-main() function handles actual execution of code by calling
appropriate private functions.
-adminView returns a public interface.

Misc. Changes:
-All references to generic 'sliderValue', 'slider', etc., renamed to
more specific 'zoomValue', 'zoomSlider', etc.
-Added comments explaining purpose of baseZoomValue
-Normalized quotation marks to use only " in HTML and only ' in
javascript
Clean up comments

Normalize comment capitalization -- all inline comments start lowercase
and all other comments start uppercase

Add comment headers to divide code into sections
Add and update comments throughout code to explain any not obvious code

Remove unnecessary comments and debug prints