Switch to hyperspace2

Use the hs2 MC hit-and-run sampling:

1. (default) using only MC sampling and boundary (section) points (replaces the useOATheuristics concept in #11).
2. (option) using also the ellipsoids growing strategy (near-bound points shootout).

Sub-tasks:

• #50 but shift-up parallelisation levels, due to built-in parallelisation support in hs2 + re-check #26 (especially if directly supported by hs2).
• Test performance (expected to be much faster with the default, and quite faster with ellipsoids);
  • cf. OEAMC performance issue;
  • re-check HYPERSPACE's performance issue w/ yTor;

Makes deprecated: #11, #39.