Change dimensions of play button in button mixin

Add media-query for play button
Update variable values and comments

Add global variables for mobile and desktop sizes of title image and
play button
Refactor titlebar.scss #1

Delete all unnecessary breakpoints
Cleanup _variables.scss
Refactor _titlebar.scss into mobile first styles

Simplify stylings within breakpoints
Update controlbar measures and variables
Delete space between arrow indicating active tab and list
Set new responsive chapter-tab measures
Decrease size of active tab arrow
Add transition for responsive toggle icons font-size scaling
Tab header is fixed when scrolling down tab content
Fix responsive measures for info tab
Replace fixed px measure for variable to keep image ratio
Set adaptive sizes for profile icons

The default icon-font-size can be changed globally while keeping the
ratio of the icon’s height and width.
The icons resize within three different breakpoints.
Set smaller layout measures, add adaptive behavior to share tab elements

- Hide the share option images when screen size is too small.
- Set smaller layout dimensions to tab elements and share footer
Minor css fixes for controlbar
Download Tab: Gets adaptive layout and smaller dimensions
Download tab: Minor css fixes for responsive button + select
Fix css bug in titlebar

Set margin auto top and bottom to header instead of fixed sizes.
css-fix for FF in togglebar