feature: add a app create interface to the java client

[cauchy1988]

[what i need?]
As mentioned in the pegasus issue : apache/incubator-pegasus#924
we wanna to create new app in container circumstances such as docker in k8s, but it is not convenient and comfortable to add the "run.sh" and "all the executed pegasus bin files" to the docker which running business code, so we think that pegasus need an app create interface

[what i will do]
i will add two new interface to the java client which are 'createApp' and 'isAppHealthy';

1. The 'createApp' interface‘s logic is almost the same with the 'replication_ddl_client.h'
2. The reason why 'isAppHealthy' interface is needed is that we can not make sure that the newly created app is fully healthy after the successful calling of 'createApp' interface；users need this interface to ensure each partition of the newly created app has enough replicas;

[how can i do]
I will reuse the 'MetaSession' class which already in the java client to send the ’RPC_CM_CREATE_APP‘ rpc to the server side， And considering the two added interface has 'timeoutMs' parameter, I refactor this class code simply;