This ticket implements submanifolds immersed or embedded in topological or differentiable manifolds.

It doesn't yet implement calculations on these submanifolds, but can find coordinates adapted to a foliation, which is the first step in 3+1 formalism in general relativity.

This is part of the ​SageManifolds project; see the metaticket #18528 for an overview.

CC: @egourgoulhon @tscrim

Component: geometry

Keywords: submanifold, embedding, immersion

Author: Florentin Jaffredo

Branch/Commit: eb2b4c8

Reviewer: Eric Gourgoulhon, Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/25164