Change Trainer SPI-return trained model & Add test cases for Encog and Spark PMML adapter

shifu-core:
1. SPI: change Trainer interface and return the trained model.
2. core.container: add SVMParams for svm model
3. core.pmml: fix bug in PMMLCommonUtil in pmml folder
shifu-plugin-*
 add test cases for Encog and Spark PMML adapter, add EncogLRTrainer.