Enhances client to support unique meter retrieval

https://review.openstack.org/272633
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commit c45000c7594ad6fbfabf44c0615dce3021f43605
Author: Rohit Jaiswal <email address hidden>
Date: Tue Jan 26 08:36:43 2016 -0800

    Enhances client to support unique meter retrieval

    meter list API is enhanced to support a unique param
    If specified as True, it returns a unique list of
    meters.

    This patch enhances the ceilometer-client to support
    the unique argument in the shell and the client bindings.

    DocImpact
    Closes-Bug: #1506959

    Change-Id: I011ca725c25e1cdbe9891c3719f13f5cd34142ea