Update the new bookkeeper tools to use the new framework

[sijie]

Descriptions of the changes in this PR:

Motivation

#1471 introduces a new tools framework based on jcommander. This PR is changing the new bookkeeper-tools to leverage that framework.

Solution

• Changed the related classes to use the new framework.
• Rename BookKeeperCLI to BKCtl and bookkeeper-cli to bkctl
• Use service loader to load command groups to allow better extensibility
• Rename command group cluster to bookies

Results

Example output of this change:

$ bin/bkctl
bkctl interacts and operates Apache BookKeeper clusters

Usage:  bkctl [flags] [command group] [commands]

Commands:

    bookie      Commands on operating a single bookie
    bookies     Commands on operating a cluster of bookies
    ledger      Commands on interacting with ledgers

    help        Display help information about it

Flags:

    -c, --conf
        Configuration file

    -u, --service-uri
        Service Uri


    -h, --help
        Display help information

Use "bkctl [command] --help" or "bkctl help [command]" for more information
about a command

sub command

$ bin/bkctl help bookie
Commands on operating a single bookie

Usage:  bkctl bookie [command] [command options]

Commands:

    lastmark        Print last log marker

    help            Display help information about it

Use "bkctl bookie [command] --help" or "bkctl bookie help [command]" for more
information about a command

sub-sub command

$ bin/bkctl bookie help lastmark
Print last log marker

Usage:  bkctl bookie lastmark [flags]

Flags:


    -h, --help
        Display help information