Is your feature request related to a problem? Please describe.
Every setlist can be used to create a new setlist via the duplicate-button. However there are use cases, where you just want to choose songs from a predefined set.

Describe the solution you'd like

• There should be 2 types of setlist: setlists (as already implemented) and template lists
• On creation of a setlist, you can choose to set it as template
• On the setlists overview page, there should be a filter (or tab navigation) to show all template lists
• On creation of a setlist, you can choose a template setlist which only provides the defined songs to choose from