enh(core): update whole documentation for sight 21.0
This is an initial update of the documentation to Sight 21.0. A mass replace has been applied to rename namespaces, classes, etc... It is probably not 100% complete but the rest will be fixed with individual tickets before the release. Closes #46 Merge branch '46-core-update-whole-documentation-for-sight-21-0' into 'dev' See merge request !35