Merge branch 'f-pam-usersource-caching' into 'dev'

conf/core/cache.ccf

conf/core/log4j2-default.properties

conf/core/server.conf

makefile

src/main/java/caosdb/server/ServerProperties.java

src/main/java/caosdb/server/accessControl/Pam.java

src/main/java/caosdb/server/accessControl/UserSource.java

src/main/java/caosdb/server/caching/Cache.java

src/main/java/caosdb/server/caching/CacheHelper.java

src/main/java/caosdb/server/caching/JCSCacheHelper.java

...a/caosdb/server/database/CacheableBackendTransaction.java

...rver/database/backend/transaction/DeleteSparseEntity.java

...ver/database/backend/transaction/GetFileRecordByPath.java

.../server/database/backend/transaction/RetrieveParents.java

...database/backend/transaction/RetrievePermissionRules.java

...rver/database/backend/transaction/RetrieveProperties.java

...sdb/server/database/backend/transaction/RetrieveRole.java

...er/database/backend/transaction/RetrieveSparseEntity.java

...abase/backend/transaction/RetrieveTransactionHistory.java

...sdb/server/database/backend/transaction/RetrieveUser.java