make the sample in Sd-factory and C.50 compileable (closes #1205, #1488) (#1489)

make the sample in Sd-factory and C.50 compileable (closes #1205, #1488) (#1489)

* make the sample in Sd-factory compileable (closes #1488)

- make the sample in Sd-factory compileable
  - fixed wrong capitalization: create/Create -> create
  - `make_shared` cannot access protected constructors, so made them public. To still have access protection introduced a protected `class Token` in each class. That token can only be created by the class itself (and derived classes) and needs to be passed to the constructor.
- changed order: `public` first, then `protected`
- same sample for C.50 and Sd-factory
- removed spurious "see Item 49.1" as it is unclear what this means

* line length

* tabs -> spaces

* spelling

* input from cubbimew

- added back in Item 49.1
- added link for items as suggested ("in [SuttAlex05](#SuttAlex05)")

* changed link to Item 49.1 to link to C.82