[GL] Make data structures more indepent from each other.

See merge request ogs/ogs!3662

Explanation is here: https://eigen.tuxfamily.org/dox/group__TopicStlContainers.html

Using Eigen::Vector3d allows some nice shortening
of the code.

- access the minimal / maximal point of the AABB
  via public interface functions.
- Using auto for minimal / maximal point to
  get independent from the point type.

- don't modify the bounding box in SurfaceGrid
- access the minimal / maximal point of the AABB
  via public interface functions.
- Using auto for minimal / maximal point to
  get independent from the point type.

[ML] Preload mfront libraries on Linux.

Closes #3073 and #3037

See merge request ogs/ogs!3663

Fixes #3073.

Small unrelated fixes almost all in GeoLib

See merge request ogs/ogs!3661

New Process: Non-isothermal Richards  flow

See merge request ogs/ogs!3419

LIS fixes

See merge request ogs/ogs!3660

Remove caching of GlobalMatrix and GlobalVector objects.

See merge request ogs/ogs!3659

[Web] Web documentation of the parallel-plate testcase.

See merge request ogs/ogs!3658