Add starter code for unified CLI [WIP]

[havanagrawal]

This is a WIP PR for discussing approach, design and implementation of resolving issue #139

[coveralls]

Pull Request Test Coverage Report for Build 506

• 6 of 13 (46.15%) changed or added relevant lines in 1 file are covered.
• 197 unchanged lines in 12 files lost coverage.
• Overall coverage decreased (-0.3%) to 89.145%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
spotpy/unittests/test_cli.py	6	13	46.15%

Files with Coverage Reduction	New Missed Lines	%
spotpy/algorithms/sa.py	1	82.86%
spotpy/algorithms/mle.py	1	91.84%
spotpy/algorithms/dream.py	1	89.0%
spotpy/algorithms/abc.py	2	89.72%
spotpy/database.py	2	88.46%
spotpy/algorithms/fscabc.py	3	83.33%
spotpy/algorithms/demcz.py	5	91.35%
spotpy/parameter.py	7	97.0%
spotpy/unittests/test_describe.py	15	95.0%
spotpy/unittests/test_gui_mpl.py	25	93.75%

Totals
Change from base Build 505:	-0.3%
Covered Lines:	4993
Relevant Lines:	5601

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💛 - Coveralls

[thouska]

Hi @havanagrawal,
i think the use of a command line interface to spotpy is now possible given the pull request #174 by @philippkraft. This should also solve #139.
Less work for you :) Feel free to give it a try.