Resolve "Urls in confimation email contains the /django/ prefix"

Closes #852

See merge request !1253

Resolve "Improve performance of polling queries"

Closes #847

See merge request !1252

Resolve "Fix whoAmI query" (and make permission query poll)

Closes #860

See merge request !1250

Resolve "Doc for maintainance tasks still mentions yarn install"

Closes #861

See merge request !1251

Merge branch '856-language-select-uses-english-as-default-language-and-not-browser-language' into 'master'

Resolve "Language select uses English as default language (and not browser language)"

Closes #856

See merge request !1245

Merge branch 'master' into '856-language-select-uses-english-as-default-language-and-not-browser-language'

# Conflicts:
#   CHANGELOG.rst

Resolve "Fix metrics URL (/django/)"

Closes #858

See merge request !1246

# Conflicts:
#   CHANGELOG.rst

Resolve "Update material design icons"

Closes #851

See merge request !1242

Resolve "Include dynamic titles in app bar of new SPA"

Closes #859

See merge request !1243

# Conflicts:
#   CHANGELOG.rst
#   aleksis/core/frontend/index.js