We only use the solid icons.

This reverts commit 924e825e.

Non-JS version still needs work. We need to review also non-iframe logout.

We have some defaults, but now we can also pass the colors to the build script like this:

npx webpack -p --env.primaryBackground=#XXX --env.transitionBackground=#YYY --env.secondaryBackground=#ZZZi

This builds and minifies CSS and a common JS bundle, as well as copy the relevant fonts. In order to build, we now need to run "npm run build" after installing the dependencies with "npm install".