Add all the strings that had no translation.

git-svn-id: svn://svn.icculus.org/fs2open/trunk/fs2_open@9600 387891d4-d844-0410-90c0-e4c51a9137d3
Have another go at fixing Mantis 2818, this time using the less fatal Warning() report in Debug builds when invalid handles passed to bm_is_valid()

git-svn-id: svn://svn.icculus.org/fs2open/trunk/fs2_open@9601 387891d4-d844-0410-90c0-e4c51a9137d3
Fix Mantis 2811 (Default Campaign File Name was not used). 

git-svn-id: svn://svn.icculus.org/fs2open/trunk/fs2_open@9602 387891d4-d844-0410-90c0-e4c51a9137d3
Third shot at Mantis 2818, other sections of the code in modelinterp.cpp use -1 is odd ways but nonetheless valid ways

git-svn-id: svn://svn.icculus.org/fs2open/trunk/fs2_open@9603 387891d4-d844-0410-90c0-e4c51a9137d3