Merge branch 'develop' (read more)

Deleted in the merge:
* combat_management.cpp
* todo.txt

Amended in the merge:
* server/enemy_factory_interface.hpp
* server/server_application.hpp
* server/server_internals.cpp

That version of combat_management.cpp was not what I was looking for. I'll
try again, this time by working my way down from SerialPacket. It's worked
in the past as far as establishing a standard goes.

todo.txt was deleted in this commit, but will be carried over into the
next develop branch.

I'll release a new demo build without changing the version number, since
there are no functional changes.