Dms-tools

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* Fixed bug in ``dms_merge``, where normalization of prefs or diffprefs was not occurring when the user provided two or more identical pref or diffpref files

* Added y-axis label override option in ``plot.PlotDepth()`` and corrected ``dms_summarizealignments`` to label the y-axis as 'number of barcodes' when summarizing barcoded subamplicon data.

* Added ``merge_method`` choice ``rescale`` to ``dms_merge`` to rescale a preferences file by a ``--stringencyparameter``.

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* Added option to trim reads R1 and R2 in ``dms_barcodedsubamplicons``

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* Fixed algorithm to estimate preferences and differential preferences using the ``--ratio_estimation`` option for both ``dms_inferprefs`` and ``dms_inferdiffprefs``.

* Fixed small bug in *dms_tools.file_io.WriteDiffPrefs* and in test suite.

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* ``dms_logoplot`` can now handle sites numbers that don't go sequentially starting with one or zero.

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* Added ``--stringencyparameter`` option to ``dms_logoplot``.

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* Added additional options for logo plots showing preferences and differential preferences