MAINT: cleanup unused classes

src/main/java/org/caosdb/server/CaosDBServer.java

...n/java/org/caosdb/server/database/BackendTransaction.java

...se/backend/implementation/MySQL/MySQLInsertLogRecord.java

.../backend/implementation/MySQL/MySQLRetrieveLogRecord.java

...rver/database/backend/interfaces/InsertLogRecordImpl.java

...er/database/backend/interfaces/RetrieveLogRecordImpl.java

.../server/database/backend/transaction/InsertLogRecord.java

...erver/database/backend/transaction/RetrieveLogRecord.java

...n/java/org/caosdb/server/resource/ServerLogsResource.java

...caosdb/server/transaction/InsertLogRecordTransaction.java

...osdb/server/transaction/RetrieveLogRecordTransaction.java