abstraction: make type-fixed ObjectFactoryImpl's not inlined + extern a common templated instantiation

Closes #49

unique ptr is convertible to shared ptr natively. It makes sense to construct
unique_ptr first and convert it to shared_ptr if it is needed.

Most likely a remnant of abstraction refactoring to OperationAbstraction and
Value where Value is using the functionality, not the OperationAbstraction

std::result_of is deprecated in C++17

Jan Trávníček authored 3 years ago and Jan Trávníček committed 3 years ago

breaking change!

While working on webui, I have noticed that exports from
automata-library contain for many algorithms documentation set to
string "Documentation not available.". I traced the problem back to this
project.

I do not think "Documentation not available" is itself a valid
documentation of an algorithm so I decided to replace the std::string
that is supposed to hold documentation of an overload with an
std::optional<std::string>. The semantics should now be clearer.

While working on a webui I noticed that some algos have documentation
set to "Documentation not avaiable" instead of available. That's a typo
with multiple occurrences throughout the project.