add preferences

app/components/nav/topbar.hbs

app/components/preferences/index.hbs

app/components/preferences/preference/index.hbs

app/components/preferences/preference/index.js

app/components/preferences/section/index.hbs

app/components/preferences/section/index.js

app/router.js

app/routes/authenticated/document.js

app/routes/authenticated/preferences/index.js

app/routes/authenticated/preferences/section.js

app/routes/authenticated/tag.js

app/services/requests.js

app/styles/app.scss

app/styles/preferences.scss

app/templates/authenticated/preferences/index.hbs

app/templates/authenticated/preferences/section.hbs