Feature: replace appendToBody by Teleport

[mlmoravek]

Description

Several components (Autocomplete, Dropdown, Datepicker, DateTimepicker, Timepicker, Tooltip) use an appendToBody feature that allows the component to be attached to the body instead of the actual position.

Vue provides a native Teleport component that allows you to "teleport" a component to another location in the dom. This could be used to provide a simpler and Vue-native implementation of the appendToBody feature.

However, some components could also benefit from having such an appendToBody feature, such as the Modal or Sidebar component.

The teleport feature needs to move the whole component and not just parts of it, because template classes could depend on parent ones, for example menu depends on its wrapper, as jtommy mentioned here #487.