change the bookieServer cmdline to make conf-file and option co-exist

[jiazhai]

Currently, when using bookieServer cmdline to start a bookie, you will either give it a cofiguration file by "-c booke.conf"; or add some options like "<bookie_port> <zk_servers> <journal_dir> <ledger_dir [ledger_dir]>" in a fix sequential. It may not satisfy some of the requirement. So changed it to be co-exist for configuration file and options.

By this change, it will first use settings in configuration file; and then use options to overwrite some of the settings, if there are some options provided.

Here is an example after this change: BookieServer -c bookie.conf -z localhost:2181 -m /bookkeeper/ledgers -p 3181 -j /mnt/journal -l "/mnt/ledger1 /mnt/ledger2 /mnt/ledger3” Here, in this command: -z is for “Zookeeper client instance”; -m is for "Zookeeper ledgers root path for bookies";
-p is for "bookie service port exported";
-j is for "bookie journal directory";
-l is for "bookie ledgers directories".

[sijie]

@jiazhai looks good to me.

[jiazhai]

@sijie Thanks for the review, looking forward to be merged.

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