CPACS 2.3.1

Release in Jul 2016

• CPACS 2.3.1 is a beta release, all parameters may be subject to change.
• Added a branch for the definition of design studies.
• Added thermal properties for materials.
• Revised the definition of flights/flightplans.
• Added an airline definition.
• Added structure for skid gear components.
• Changed the units for material density to SI units.
• Revised the top level fleets node and put it into the new airline node.
• All issues for this release can be found online
• https://github.com/DLR-LY/CPACS/issues