webapi: moves amqp-api and cli-api under common/engine/

...servlet/src/main/java/common/engine/amqp/JsonDecoder.java

...servlet/src/main/java/common/engine/amqp/JsonEncoder.java

...et/src/main/java/common/engine/amqp/JsonEncoderMerge.java

...servlet/src/main/java/common/engine/amqp/RpcOverAmqp.java

...cess/servlet/src/main/java/common/engine/cli/ExecCmd.java