implement Project, ProjectFile and ProjectFolder in rust

[rbran]

I assumed that BNProjectFileGetCreationTimestamp and other time related fields are seconds since the UNIX_EPOCH.

I also notice that the CPP implementation is missing the functions BNFreeProject, BNFreeProjectFile and BNFreeProjectFolder, although it include the implementation for each of these objs. Maybe it's missing the deconstructor and is leaking memory.

[rbran]

NOTE TO SELF: Once merged, remember to rebase and PR rbran/impl-external-l

[negasora]

Manually rebased and pushed these commits, ty!