More robust error logging.
Fixed absence of output
Fixed create command arguments
Fixed signature.tsv format
Implemented TableSignature.toString() and simplified code
Nice formatting in show tables
Added signs method to display signatures of tables
Commit and rollback now show number of uncommited changes
Structured put now supports spaces in serialized string
Commas in json strings now supported.
Added comma test in SerializationTest
Added more tests
Renamed test files
Merge branch 'task6' into task7

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