SSDM-3907: First implementation of a specialized structure. On my way to ftp plugins

...sd/openbis/dss/generic/server/ftp/NonExistingFtpFile.java

.../dss/generic/server/ftp/v3/V3ExperimentLevelResolver.java

.../dss/generic/server/ftp/v3/V3FtpPathResolverRegistry.java

.../generic/server/ftp/v3/V3HierarchicalContentResolver.java

...d/openbis/dss/generic/server/ftp/v3/V3PluginResolver.java

...bis/dss/generic/server/ftp/v3/V3ProjectLevelResolver.java

...sx/cisd/openbis/dss/generic/server/ftp/v3/V3Resolver.java

...penbis/dss/generic/server/ftp/v3/V3RootLevelResolver.java

...enbis/dss/generic/server/ftp/v3/V3SpaceLevelResolver.java

...ss/generic/server/ftp/v3/file/V3FtpDirectoryResponse.java

...isd/openbis/dss/generic/server/ftp/v3/file/V3FtpFile.java

...bis/dss/generic/server/ftp/v3/file/V3FtpFileResponse.java

.../dss/generic/server/ftp/v3/file/V3FtpNonExistingFile.java