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.

moving is actually more expensive for shared_ptrs

Remove CMakeLists.txt generator scripts from build phase. Replaced with
CMake's GLOB that can re-run every time the build is invoked. We can
also drop the Python dependency now.

Removed header installs which will be redesigned in future commits.