SP-387, BIS-255: extracting IContentCache interface in order to fix dependency problem

...DataSetAndPathInfoDBConsistencyCheckProcessingPlugin.java

...enbis/dss/generic/shared/HierarchicalContentProvider.java

...emsx/cisd/openbis/dss/generic/shared/ServiceProvider.java

...cisd/openbis/dss/generic/shared/content/ContentCache.java

...isd/openbis/dss/generic/shared/content/IContentCache.java

...dss/generic/shared/content/RemoteHierarchicalContent.java

...generic/shared/content/RemoteHierarchicalContentNode.java

...penbis/dss/generic/server/DatasetDownloadServletTest.java

.../cisd/openbis/dss/generic/server/DssServiceRpcV1Test.java

...s/dss/generic/shared/HierarchicalContentProviderTest.java

...ed/content/AbstractRemoteHierarchicalContentTestCase.java

...content/RemoteHierarchicalContentNodeMultiThreadTest.java

...ric/shared/content/RemoteHierarchicalContentNodeTest.java

...generic/shared/content/RemoteHierarchicalContentTest.java