Theme: initial integration of CSS for base WET Theme

- Partial cleanup up of base SCSS

- Changed dist/demo directory to dist/demos to align with existing v3.1 folder structure

- Now generating license files and update generated home files

- Updated build to move assets and plugin files to the new dist/demos directory

- Corrected duplication of accessiblity placeholders

- Removed sr-only trailing reference

Removed redundant accessiblity file
Fix Bad merge resolution
Test: added local Mocha testing with grunt-mocha
Test: updated session timeout selector unit test
Test: added Prettify unit tests
Merge pull request #3264 from patheard/prettify-test

Test: added Prettify unit tests
Merge pull request #3254 from patheard/grunt-mocha

Test: added local Mocha testing with grunt-mocha
Twitter embedded timeline: Fixed loading of dependency
Merge pull request #3271 from pjackson28/twitterfix

Twitter embedded timeline: Fixed loading of dependency
WET theme: Numerous tweaks to the visuals
Merge pull request #3272 from pjackson28/themecleanup

WET theme: Numerous tweaks to the visuals
WET theme: Cleaned up minor formatting issues
Merge pull request #3277 from pjackson28/morewetthemetweaks

WET theme: Cleaned up minor formatting issues
Optimized vapour.js Modernizr prefixing and now loading polyfill CSS
Merge pull request #3279 from pjackson28/integrationofpolyfillscss

Optimized vapour.js Modernizr prefixing and now loading polyfill CSS
Build: Flatten dist directory on wet-boew-dist
Merge pull request #3282 from nschonni/v4-flatten-dist-on-publish

Build: Flatten dist directory on wet-boew-dist
Datalist polyfill: Cleaned up display and event handling
Details polyfill: Rewrote polyfill, added CSS and working examples
Merge pull request #3283 from pjackson28/detailspolyfillcleanup

Details polyfill: Rewrote polyfill, added CSS and working examples