Vuetify refactor

[jptissot]

fixes #296

fix: login layout theme

feat: Vuetify module

• Move most widgets to the Vuetify module
• Create features for each group of widgets (Grid for example)
• Move placement.json to Vuetify module instead of admin theme
• Add CustomClass property to flow widgets
• Add logo that displays on smaller viewports for Vuetify theme

chore: remove deprecated vuetify saas recipe

fix: wording / style for login & registration

fix: display labels in the widget settings modal