Restructuring Python bindings, moved submodules and dependencies to own folders, added dependency checking for some tutorials, minor refactorings

Former-commit-id: 2214125878

python/python_shared.cpp

@@ -14,6 +14,18 @@ extern void python_export_igl_viewer(py::module &);
 extern void python_export_igl_comiso(py::module &);
 #endif
 
+#ifdef PY_TETGEN
+extern void python_export_igl_tetgen(py::module &);
+#endif
+
+#ifdef PY_EMBREE
+extern void python_export_igl_embree(py::module &);
+#endif
+
+#ifdef PY_TRIANGLE
+extern void python_export_igl_triangle(py::module &);
+#endif
+
 PYBIND11_PLUGIN(pyigl) {
     py::module m("pyigl", R"pyigldoc(
         Python wrappers for libigl
@@ -39,5 +51,17 @@ PYBIND11_PLUGIN(pyigl) {
     python_export_igl_comiso(m);
     #endif
 
+    #ifdef PY_TETGEN
+    python_export_igl_tetgen(m);
+    #endif
+
+    #ifdef PY_EMBREE
+    python_export_igl_embree(m);
+    #endif
+
+    #ifdef PY_TRIANGLE
+    python_export_igl_triangle(m);
+    #endif
+
     return m.ptr();
 }