add AI_CONFIG_IMPORT_MD3_LOAD_SHADERS bool option

the purpose is use of this loader with idtech3 FS
this requires full original material name, which euqals to Q3 shader path
result of deduction is not usable inside Q3 FS at all
option in general is "do not tinker with the path"

code/AssetLib/MD3/MD3Loader.cpp

@@ -450,6 +450,9 @@ void MD3Importer::SetupProperties(const Importer *pImp) {
     // AI_CONFIG_IMPORT_MD3_SKIN_NAME
     configSkinFile = (pImp->GetPropertyString(AI_CONFIG_IMPORT_MD3_SKIN_NAME, "default"));
 
+    // AI_CONFIG_IMPORT_MD3_LOAD_SHADERS
+    configLoadShaders = (pImp->GetPropertyBool(AI_CONFIG_IMPORT_MD3_LOAD_SHADERS, true));
+
     // AI_CONFIG_IMPORT_MD3_SHADER_SRC
     configShaderFile = (pImp->GetPropertyString(AI_CONFIG_IMPORT_MD3_SHADER_SRC, ""));
 
@@ -781,7 +784,9 @@ void MD3Importer::InternReadFile(const std::string &pFile, aiScene *pScene, IOSy
 
     // And check whether we can locate a shader file for this model
     Q3Shader::ShaderData shaders;
-    ReadShader(shaders);
+    if (configLoadShaders){
+        ReadShader(shaders);
+    }
 
     // Adjust all texture paths in the shader
     const char *header_name = pcHeader->NAME;
@@ -863,7 +868,12 @@ void MD3Importer::InternReadFile(const std::string &pFile, aiScene *pScene, IOSy
 
         std::string convertedPath;
         if (texture_name) {
-            ConvertPath(texture_name, header_name, convertedPath);
+            if (configLoadShaders){
+                ConvertPath(texture_name, header_name, convertedPath);
+            }
+            else{
+                convertedPath = texture_name;
+            }
         }
 
         const Q3Shader::ShaderDataBlock *shader = nullptr;