Xtrack version 0.6.0

New features:

• Introduced Tracker.cycle
• Introduced Tracker.twiss
• Introduced Tracker.filter_elements
• Configuration of space-charge lenses is done using Tracker.twiss instead of MAD-X
• Particles for footprint example are generated using xpart
• knl and ksl in Multipole and RFMultipole are linked to bal using xobject.LinkedArray

Other:

• Clean up examples for direct use in documentation
• Tests introduced for mad-x loader, energy ramp, ring with space charge (frozen, quasi-frozen and PIC)
• Added test_data with precisely matched HL-LHC lattice