message: More context in error message when import text fails
diff: @@ -1041,6 +1041,7 @@ struct ImportTextProcedureWorkInstance
  int chunkNum,
  int64_t lineNum)
  {
  + try {
  auto & threadAccum = accum.get();
  threadAccum.linesDone += 1;
  @@ -1299,6 +1300,13 @@ struct ImportTextProcedureWorkInstance
  }
  return true;
  + } MLDB_CATCH_ALL {
  + rethrowException(400, "Error parsing CSV line",
  + "lineNumber", lineNum + lineOffset,
  + //"line", std::string(line, length),
  + "dataFileUrl", config.dataFileUrl);
  + }
  + return false;
  };
  