Added png compression task

```
Running "pngmin" task
>> Compressed 8 files
>> Uncompressed size: 186kb, Compressed size: 25.76kb, Savings: 86.15%
```
Hide menu when it hasn't been called up.
Merge pull request #3716 from thomasgohard/fix-menu-css

Fix for issue #3715
WET theme: Fixed site title link (fixes #3718)
Toggle: plugin behaviour fixes

1. Fix first click on elements that toggle themselves.
2. Fix setAriaControls to set unique IDs on elements that don't
   have an ID defined.
3. Group toggle elements no longer default to "type: on" (fixes #3711)
Toggle: update examples to show group with "type: on"
Merge pull request #3719 from pjackson28/fixsitetitlelink

WET theme: Fixed site title link (fixes #3718)
Merge pull request #3720 from patheard/accordion

Toggle: plugin behaviour fixes
Share: All panel and link markup now auto-generated
Merge pull request #3724 from pjackson28/fixshare

Share: All panel and link markup now auto-generated
Fixed mistaken replacements with 'panel'.
Tabs & multimedia: Fixed various wrong/broken links in HBS files.
Overlay: Added escape handling
Merge pull request #3726 from pjackson28/addescapetooverlay

Overlay: Added escape handling
Merge pull request #3725 from thomasgohard/fix-share-panel-replacements

Share: Fixed mistaken replacements with 'panel'
Merge pull request #3727 from EricDunsworth/v4.0-broken-link-fixes

Tabs & multimedia: Fixed various wrong/broken links in HBS files.
Accessibility Responsiblity Breakdown: Added option to limit the number of visible entries (fixes #3721)
Merge pull request #3730 from pjackson28/arboption

Accessibility Responsiblity Breakdown: Added option to limit the number of visible entries (fixes #3721)
Overlay: Added overflow: auto and max-height: 100% to resolve issue with overlay being taller than the viewport
Merge pull request #3731 from pjackson28/improveoverlay

Overlay: Added overflow: auto and max-height: 100% to resolve issue with overlay being taller than the viewport