Added missing README file

README.md

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+# Document Store Backend Connector Library for PostgreSQL
+
+Document Store Backend Connector Library for PostgreSQL
+
+## Built With
+
+* [OpenJDK](https://openjdk.java.net/) - The JDK used
+* [Maven](https://maven.apache.org/) - Dependency Management
+
+## Documentation
+
+[Document Store Backend Connector Library for PostgreSQL](https://wiki.gcube-system.org/gcube/Document_Store_Library)
+
+## Change log
+
+See [Releases](https://code-repo.d4science.org/gCubeSystem/document-store-lib-postgresql/releases).
+
+## Authors
+
+* **Luca Frosini** ([ORCID](https://orcid.org/0000-0003-3183-2291)) - [ISTI-CNR Infrascience Group](http://nemis.isti.cnr.it/groups/infrascience)
+
+## How to Cite this Software
+
+Tell people how to cite this software. 
+* Cite an associated paper?
+* Use a specific BibTeX entry for the software?
+
+
+	@Manual{,
+		title = {Document Store Backend Connector Library for PostgreSQL},
+		author = {{Frosini, Luca}},
+		organization = {ISTI - CNR},
+		address = {Pisa, Italy},
+		year = 2021,
+		url = {http://www.gcube-system.org/}
+	} 
+
+## License
+
+This project is licensed under the EUPL V.1.2 License - see the [LICENSE.md](LICENSE.md) file for details.
+
+
+## About the gCube Framework
+This software is part of the [gCubeFramework](https://www.gcube-system.org/ "gCubeFramework"): an
+open-source software toolkit used for building and operating Hybrid Data
+Infrastructures enabling the dynamic deployment of Virtual Research Environments
+by favouring the realisation of reuse oriented policies.
+ 
+The projects leading to this software have received funding from a series of European Union programmes including:
+
+- the Sixth Framework Programme for Research and Technological Development
+    - DILIGENT (grant no. 004260).
+- the Seventh Framework Programme for research, technological development and demonstration 
+    - D4Science (grant no. 212488);
+    - D4Science-II (grant no.239019);
+    - ENVRI (grant no. 283465);
+    - iMarine(grant no. 283644);
+    - EUBrazilOpenBio (grant no. 288754).
+- the H2020 research and innovation programme 
+    - SoBigData (grant no. 654024);
+    - PARTHENOS (grant no. 654119);
+    - EGIEngage (grant no. 654142);
+    - ENVRIplus (grant no. 654182);
+    - BlueBRIDGE (grant no. 675680);
+    - PerformFish (grant no. 727610);
+    - AGINFRAplus (grant no. 731001);
+    - DESIRA (grant no. 818194);
+    - ARIADNEplus (grant no. 823914);
+    - RISIS2 (grant no. 824091);
+
+