Implement return policies.
dllexport StackRestore.
Fix const-ness of return policy.
Enable return policy for Execute().
Fix StackRestore initialization.
Pass return policy by value.
Fix comment typo and indicate remaining returns.
Allow Execute() to return values on the stack.
Fill in missing param doc.
Add dummy session.lua for require().
Make LoadChunkFromFile protected and static.
Add PassReturn return policy.
Actually run the file from require().
Fix rulebook name in library.

The "real" name of the rulebook (as loaded from the rulebook's metadata,
not from the directory name) hadn't been loaded yet before we added it
to the map.