Ds 3552 read only context and hibernate improvements (#1694)

* Refactor READ ONLY mode in Context and adjust hibernate settings accordingly

* Set Context in READ-ONLY mode when retrieving community lists

* Fix Hibernate EHCache configuration + fix some Hibernate warnings

* Cache authorized actions and group membership when Context is in READ-ONLY mode

* Set default Context mode

* Let ConfigurableBrowse use a READ-ONLY context

* Add 2nd level cache support for Site and EPerson DSpaceObjects

* Added 2nd level caching for Community and Collection

* Fix tests and license checks

* Cache collection and community queries

* Small refactorings + backwards compatibility

* Set Context to READ-ONLY for JSPUI submissions and 'select collection' step

* OAI improvements part 1

* OAI indexing improvements part 1

* OAI indexing improvements part 2

* DS-3552: Only uncache resource policies in AuthorizeService when in read-only

* DS-3552: Additional comment on caching handles

* DS-3552: Fix cache leakage in SolrServiceResourceRestrictionPlugin

* DS-3552: Clear the read-only cache when switching Context modes

* DS-3552: Correct Group 2nd level cache size

* DS-3552: Always clear the cache, except when going from READ_ONLY to READ_ONLY

dspace-api/src/main/java/org/dspace/content/Community.java

@@ -34,6 +34,8 @@ import java.util.*;
  */
 @Entity
 @Table(name="community")
+@Cacheable
+@org.hibernate.annotations.Cache(usage = CacheConcurrencyStrategy.NONSTRICT_READ_WRITE, include = "non-lazy")
 public class Community extends DSpaceObject implements DSpaceObjectLegacySupport
 {
     /** log4j category */