Xtrack version 0.88.0

Changes:

• Introduce support for XRotation, YRotation, SRotation, XYShift in Line.survey(...)
• Introduce rbend_model allowing to switch between straight-body and curved-body for RBend elements
• Support URL and json.gz in Environment.vars.load(...)
• Fixes in RBend.__init__(...) and Bend.__init__(...)
• Fix in Edwards-Teng coupling computation

Full Changelog: v0.87.1...v0.88.0