assign unique ids to components

[langehm]

          We should introduce a composable to define unique id's automagically to every html element. Ussage like the following:

const idForThisComponent = useUniqueID("muc-radio-button"); // return sth like muc-radio-button-123

vuetify uses similiar approach with some vue methods to generate the unique id's.

Originally posted by @langehm in #101 (comment)