MESH: Modify tolerance for `.contains()` under manifold case

[AlePalu]

In the implementation of .contains() under the manifld case, a point is considered as part of a mesh element if its L2 distance from the space where the element belongs is under the machine epsilon.
This requirement might be too strict. We can set an higher treshold from std::numeric_limits<double>::epsilon() to a multiple of this quantity.

For example 10*std::numeric_limits<double>::epsilon() might be a good choice.

[AlePalu]

This is solved in 5898f4a.
Tolerance is now set to 10*std::numeric_limits<double>::epsilon().

Closing