finish save to and load from json

.gitignore

src/main/java/com/ic/er/Attribute.java

src/main/java/com/ic/er/ER.java

src/main/java/com/ic/er/Entity.java

src/main/java/com/ic/er/LayoutInfo.java

src/main/java/com/ic/er/Relationship.java

src/main/java/com/ic/er/Trans.java

src/main/java/com/ic/er/View.java

src/main/java/com/ic/er/common/RelatedObjType.java

src/main/java/com/ic/er/common/RelationshipSerializer.java

src/main/java/com/ic/er/common/Trans.java

src/main/java/com/ic/er/common/ViewDeserializer.java

src/main/java/com/ic/er/dao/GraphInfoMapper.java

src/main/java/com/ic/er/dao/LayoutInfoMapper.java

src/main/java/com/ic/er/entity/LayoutInfoDO.java

src/main/resources/mapper/LayoutInfoMapper.xml

src/main/resources/mybatis-config.xml

src/main/resources/sql/schema-v1.sql

src/test/java/com/ic/er/TestAttribute.java

src/test/java/com/ic/er/TestER.java