SSDM-13251: Added support for write, copy and move methods. Refactored tests

...src/main/java/ch/ethz/sis/afsclient/client/AfsClient.java

...test/java/ch/ethz/sis/afsclient/client/AfsClientTest.java

...st/java/ch/ethz/sis/afsclient/client/DummyHttpServer.java

...a/ch/ethz/sis/afsserver/server/impl/ApiServerAdapter.java

...re/src/test/java/ch/ethz/sis/afsserver/ApiClientTest.java

.../ch/ethz/sis/afsserver/core/AbstractPublicAPIWrapper.java

...c/test/java/ch/ethz/sis/afsserver/core/PublicApiTest.java

...a/ch/ethz/sis/afsserver/impl/APIServerAdapterWrapper.java

...est/java/ch/ethz/sis/afsserver/impl/APIServerWrapper.java