Add README.md files for moeo/tutorial/Lesson{1-4}, smp/tutorial/Lesson{1-4},
and mo/tutorial/Lesson9 — these tutorials had no documentation.
Fix return 1 → return 0 in 28 tutorial main() functions across mo/ and
smp/ that unconditionally returned failure status.
- `std::apply` is part of C++17 and the compiler wants to use it because
of ADL. Thus it is now necessary to escape it as `::apply`.
- remove some `using namespace std` remaining in the sources.
- fix simple warnings.
