Enhance toolbar concept

[chrismayer]

The way of embedding the toolbar should become more flexible. At the moment the toolbar is a Vuetify-standard component, which is rendered at the top of the map and can be filled with buttons.

A few optimizations would be good to make the usage of toolbars more flexible:

• Support horizontal and vertical toolbars
• Let the TB contain more components than buttons, e.g. combos

This issue can be seen as a master issue, which references sub-issues:

• Group tools in a menu Group tools in a menu #33

[chrismayer]

Closed since the toolbar is way more flexible than at the point this issue was created. Further optimizations are handled in separate issues, like #118.