v0.7.5

Added
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- B-plane computation for planetary capture of flyby
- Generic Lagrange and linear interpolators

Modified
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- CCSDS : OEM and OMM optional fields are now optionals
- Consistency of API between impulsive and continuous thrusts
- Simplification of frame transition matrices
- Printing a TLE object display its name, if available
- CCSDS : TDM de-duplication of code

Fixed
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- CCSDS : OEM interpolation degree
- Improve error messages