abstract fetch function

Deleted input/get/publication_interface.py and added its functionality to input/interface.py Added a few comments Changed input/get/acs.py to accept url based on '10.1021' Changed Publication initializer to directly accept References and Citations

input/get/README.md

+# Journal Fetcher
+In this Directory there are all the Fetcher, to create an publication-instance.  
+These Fetchers should inherit from [**JournalFetcher**](journal_fetcher.py).
+
+## Template
+There is a [**template file**](template_.py) with no functionality but can be used to get to see what needs to be added.  
+
+## Naming Convention
+The filename of the fetcher should be <[a-z]+>.py and the classname should be \<Filename\>Fetcher.  
+Example:  
+filename: [acs.py](acs.py)  
+classname: [AcsFetcher](acs.py)
+
+## Format
+Fetchers should keep this format:
+- doi_url : *https://doi.org/10.xxxx/...*
+- title   : *title*
+- contributors: *[contrib_1, contrib_2, ...]*
+- journal = *full name*
+- publication_date = *dd.mm.yyyy*
+- subjects = *[subject_1, subject_2, ...]*
+- references = *[reference_1, reference_2, ...]*
+- citations = *[citations_1, citation_2, ...]*
+- abstract = *abstract without '\n'*
+
+
+## Tests
+Tests for these Modules are in **input/test/**.  
+These tests should inherit from [**FetcherTestCase**](../test/test_input.py) and should have positive and negative testcases. Look in [**test_acs.py**](../test/test_acs.py) for reference.
+There are also tests which compares the string representation of the publication with a predefined one.[*](../test/test_txt/acs.txt)
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