* 1.Remove import doris via csv in Dataxwriter, only support via json;
2.Format Dataxwriter code;
3.Optimize exception handling and reduce multiple output of exception logs;
4.Update the dataxwriter's documentation;
* Delete DorisCsvCodec.java
delete unused file extension/DataX/doriswriter/src/main/java/com/alibaba/datax/plugin/writer/doriswriter/DorisCsvCodec.java
* 1.remove `format` config key;
2.Optimize serialization code in DorisJsonCodec class
make doriswriter of DataX support format csv. Format csv is more simple and faster than
format json when data is simple
add property format: csv/json
add property column_separator: effect when format is csv, for example "\x01" , "^", etc...
