Branding: Wallet selector

Currently looking like this

Task is to match the style as seen in https://github.com/bitshares/beet/issues/34#issuecomment-441528538

Due to a build process issue (couldnt get vue sass loader to work properly) npm run buildcss needs to be run to compile global sass files.

Styling the default combobox seems obnoxious (https://css-tricks.com/dropdown-default-styling/), switching to multiselect may be warranted (as seen here https://github.com/bitshares/beet/blob/develop/src/components/account-select.vue) and adjust it's styling to match.

Either solution is fine as long as the default combobox UX flow is maintained.