Integrate KSL Weather Widget into Header

Removes the dummy weather widget from KSL Header handlebar blocks
and replaces it with the working React Weather Widget.

Updates styles to account for conflicting ddm-collapsible and
ddm-dropdown styles. The KSL Header is using the old version of
these libraries while KSL Weather Widget is using the React version
of the same libraries.

Removes unneeded background-size polyfills and the weather-icon styles.