- Moved the second leg arc recalculation to the evaluation fonction,
so it is always calculated for every trajectories, not the
bes one only. It led to wrong "best" deltaV calculations.
- Fixed the accuracy of the system time when clicking on a date displayed
in maneuver details.
- Reimplemented 2D orbital mechanics functions in physics-2d.ts
and encaspulated inside a `Physics2D` namespace.
- Deleted physics.ts and moved the required functions into physics-3d.ts
Further cleaning and reimplemntation will be done on the physics-3d.ts
content.
- Forced consistency on error handling : every raised error throws
an `Error` object.
- Commented sections relative to 2D physics and sequence generation.
