Added png compression task

```
Running "pngmin" task
>> Compressed 8 files
>> Uncompressed size: 186kb, Compressed size: 25.76kb, Savings: 86.15%
```
Overlays: Fixed z-index issue with full-screen overlay
Merge pull request #3757 from pjackson28/fixzindexfullscreenoverlay

Overlays: Fixed z-index issue with full-screen overlay
WET theme: Renamed supporting.hbs to secondarymenu.hbs
Merge pull request #3760 from pjackson28/renamesupporting

WET theme: Renamed supporting.hbs to secondarymenu.hbs
Country Content: use lower case country code for lookup

Fixes gh-3766
Data-inview / Archived: Migrated data-inview banner and archived content examples to using overlays
Merge pull request #3770 from pjackson28/overlaypersistentheaderfooter

Data-inview / Archived: Migrated data-inview banner and archived content examples to using overlays
Merge pull request #3769 from nschonni/v4-fix-country-content-3766

Country Content: use lower case country code for lookup
Country Content: Cleaned up a few typos and grammar issues
Merge pull request #3771 from pjackson28/countrytypofix

Country Content: Cleaned up a few typos and grammar issues
Archived content: Increased link size to the full size of the banner
Merge pull request #3772 from pjackson28/increasearchivetarget

Archived content: Increased link size to the full size of the banner
Tabs: Now ignores middle and right mouse button clicks
Merge pull request #3773 from pjackson28/tabsignoremiddlerightmouseclicks

Tabs: Now ignores middle and right mouse button clicks
Lightbox: Added data-wet-boew support and fixed several visual glitches
Merge pull request #3775 from pjackson28/lightboxdatawetboewsupport

Lightbox: Added data-wet-boew support and fixed several visual glitches
Tables: Removed role='grid' override
Toggle: aligned WAI-ARIA attributes with recommendation

WAI-ARIA attributes are now being set based on accordion widget
recommendations: http://www.w3.org/TR/wai-aria-practices/#accordion
Merge pull request #3776 from pjackson28/removetablesgridoverride

Tables: Removed role='grid' override