Redo Color Theme and css cleanup

* remove vars and add elements to base and btn vars
* change default border radius to 10px and padding to 0.7em
* put border radius and padding on search input form, infoxbox and buttons
* remove unused .help class in #categories_container
* remove active background from tabs to straemline design
* redo search form: 10px padding
* 2rem margin on search results on desktop
* fix modal pacement of engine reliability in prefs
* use darker accent colors
* streamline autocomplete with more padding and a hover effect