fix conflicting case sensitive paths for detective crap

--HG--
rename : code/modules/DetectiveWork/detective_work.dm => code/modules/detectivework/detective_work.dm
rename : code/modules/DetectiveWork/evidence.dm => code/modules/detectivework/evidence.dm
rename : code/modules/DetectiveWork/footprints_and_rag.dm => code/modules/detectivework/footprints_and_rag.dm