Build: Add "pages" task to alias Assemble calls

Reuse the unminified Assemble files to create the minified versions instead of
re-running the task with a different assset path.
This is done by passing the unmin files through the HTMLCompressor and then
regexing the asset paths.
Merge pull request #5478 from nschonni/single-assemble-target

Build: Rework pages building
Force display none for hidden slider polyfills
This fights specificity issue that arise by adding styles to non polyfilled slider control
Merge pull request #5493 from LaurentGoderre/fix-hidden-slider-polyfill

Force display none for hidden slider polyfills
Multimedia: Dropped the fast froward and rewind buttons
Fixes (#5175)
Made the background color for multimedia player controls lighter
Fixes #5178
Made mutlimedia player text always visible
Fixes #5173
Fixed the display of the progress bar
Added more space between the time displays
Changed the state display of the closed caption button.
Fixes #5172
Removed unused attributes in the multimedia player template
Fixed the display of the closed caption button
Added aria for the toggle buttons (mute and cc)
Optimized the SCSS for the multimedia player
Moved the mute control to the left side.
As per #5167
Moved the tabindex from the text area to the progress bar
Added volume control
Fixed the volume slider for IE11
Update the volume slider when the media is muted
Aligned the volume control in Chrome, Firefox and IE11