SSDM-1012 Archivation policy by space + refactoring of the experiment policy + unit tests

...h/systemsx/cisd/etlserver/plugins/BaseGroupingPolicy.java

...h/systemsx/cisd/etlserver/plugins/ByExpermientPolicy.java

...ava/ch/systemsx/cisd/etlserver/plugins/BySpacePolicy.java

...cisd/etlserver/plugins/grouping/DatasetListWithTotal.java

...ns/grouping/ExperimentAndDataSetTypeGroupKeyProvider.java

...tlserver/plugins/grouping/ExperimentGroupKeyProvider.java

...ch/systemsx/cisd/etlserver/plugins/grouping/Grouping.java

...d/etlserver/plugins/grouping/ProjectGroupKeyProvider.java

...stemsx/cisd/etlserver/plugins/ByExperimentPolicyTest.java

...systemsx/cisd/etlserver/plugins/ByPoliceAbstractTest.java

...ch/systemsx/cisd/etlserver/plugins/BySpacePolicyTest.java