Resolves various errors as caught by Echelon9. Mostly annoying .c_str() absences.

Fixed a logical flow error in ship.cpp where a user could forget to list a subsystem and get the error message "Unknown argument." Although perfectly valid, a more helpful error message was determined to be needed.

[amend] missed a few things
Merge branch 'debug_console' of https://github.com/z64555/fs2open.github.com into debug_console