Add Hipparchus build if necessary

The double hash is used by Velocity as a comment marker.

Conflicts:
	src/test/java/org/orekit/rugged/intersection/BasicScanAlgorithmTest.java

A new method getAlgorithmId() gives the algorithm identifier (DUVENHAGE,
CONSTANT_ELEVATION_OVER_ELLIPSOID, ...)

Fixes #381

Internally, we really use Gradient as the implementation in the library,
and DerivativeStructure in the tests for cross checks.

Fixes #385.

Fixes #386

Fixes #386

Deploy site

See merge request orekit/rugged!1

Guilhem Bonnefille authored Jun 30, 2020 and Guilhem Bonnefille committed Jun 30, 2020

Needed for using SSH key.