fix: Theming and typography (#56)

* Remove unused helper

* Fix wrong Icon reference

* Re-enable Storybook on IE11

* Update style mixins for Button

* Add Label component

* Speed-up Icon mouting

* Condense helpers

* Remove labels from CheckBox and RadioButton

* Avoid runtime string transformations

* Update theming for CheckBox, RadioButton, and ToggleSwitch

* Add Hint component; update Field, ButtonGroup, and FieldGroup

* Remove obsolete mixins

* Remove styled-components from the final bundle

* Use adimensional lengths on tokens

* Add some typographic components

* Update storybook helpers

* Update dependencies

* Autoprefix standard classes

* Rename typography module as textStyles

* Rename actions module as buttonColors

* Drop CSS variables again

* Remove some subclasses

* Add missing diplayName

* Reenable CSS vars to base theme variables

* Reattach theme variables to components