Fixed output in show tables
Removing current table now doesn't lead to undefined behaviour.
Minor fixes
Changed some synchronized method with ReadWriteLocks
Merge branch 'task6' into task7

Conflicts:
	src/ru/fizteh/fivt/students/standy66_new/storage/strings/StringDatabase.java
	src/ru/fizteh/fivt/students/standy66_new/storage/strings/StringTable.java
	src/ru/fizteh/fivt/students/standy66_new/storage/structured/StructuredDatabase.java
	src/ru/fizteh/fivt/students/standy66_new/storage/structured/table/StructuredTable.java