Fkd/lasso circle selection

[VasilisKalaitzis]

Ready for verification checklist

Please make sure to go through the list below before adding reviewers.
If some checks aren't done, you can create a draft PR until they are.

• Resolve conflicts
• Unit tests
• Manual verification

Summary

This PR adds the selection functionality with circle and lasso.

Left ToDo:

• During selection, add the ability to switch between layers (currently not supported by nebula)
• Unit tests
• (Optional) I personally don't like to have multiple function that changes the class' state. Maybe the selection-model/index.ts can become a little cleaner by not having so many (a) state variables or (b) so many functions that changes the state.