Merge branch 'master' of ssh://www.orekit.org/rugged-main

src/main/java/org/orekit/rugged/raster/UpdatableTile.java

src/main/java/org/orekit/rugged/utils/ExtendedEllipsoid.java

...java/org/orekit/rugged/utils/NormalizedGeodeticPoint.java

src/main/java/org/orekit/rugged/utils/ParameterType.java

src/main/java/org/orekit/rugged/utils/ParametricModel.java

...ava/org/orekit/rugged/utils/SpacecraftToObservedBody.java

src/site/markdown/building.md

src/site/markdown/configuration.md

src/site/markdown/contact.md

src/site/markdown/contributing.md

src/site/markdown/design/digital-elevation-model.md

src/site/markdown/design/overview.md

src/site/markdown/design/preliminary-design.md

src/site/markdown/design/technical-choices.md

src/site/markdown/downloads.md

src/site/markdown/faq.md

src/site/markdown/guidelines.md

src/site/markdown/index.md

src/site/markdown/sources.md

src/site/markdown/tutorials/direct-location-with-DEM.md