Throw exception when 'keyProperty' is missing in Jdbc3KeyGenerator.

[harawata]

Jdbc3KeyGenerator silently ignores generated keys if keyProperty is missing.

mybatis-3/src/main/java/org/apache/ibatis/executor/keygen/Jdbc3KeyGenerator.java

Lines 63 to 65 in 87c6e79

	if (keyProperties == null || keyProperties.length == 0) {
	return;
	}

It was not helpful already (e.g. #1183 ), but especially now that we fixed #1198 , users relying on the default 'keyProperty' value will experience an annoying problem with 3.5.0 i.e. assigning generated keys stops working without any error.
We should avoid it to happen.

@jeffgbutler @kazuki43zoo ,
Could you take a look and see if I am missing something, please?

[harawata]

I forgot about the PostgreSQL's funky behavior. :P
Let's hope everyone reads the release note carefully.