Support CREATE and MERGE operators

[Panghy1106]

Closes #4 Closes #5

Support CREATE and MERGE operators， templates used for testing such as:

• MATCH (n:Person {name:'Caocao'}) MERGE (n)-[r:Knows]->(m:Person {name:'Sunquan'}) RETURN r
• MERGE (a:Person {name: 'zhangsan'}) CREATE (b:Person {name : 'xiaoming'}) RETURN b