Add function to determine is the current page is using the front page template
Remove the unused Multiple Select control

Also not needed since WordPress 4.0
Customizer: Don't add Chosen.js to the categories dropdown

The section CSS has overflow: hidden so the dropdown is cut off and
might only show 1-2 options at the time.

The default select doesn’t have that problem.
Slider: Use `posts_per_page` instead of `showposts

`showposts` has been deprecated since 2.1…………….
Customizer: Move the JS to its own file
Customizer: Add live preview of the header image
Customizer: Add a new function to get all categories
Customizer: Add a new section for the slider settings
Customizer: Add a new section for the Headline settings
Customizer: Change the type of number controls to number

Supported since WordPress 4.0
Customizer settings: Remove unneeded capability

`edit_theme_options` is the default.
Customizer: Add descriptions to slider settings
Customizer: Only show additional slider settings if the slider is active
Customizer: update inline docs