added new column type/value model classes: BooleanColumn{Type,Value}. But they are now used in mysql table reader only
minor change of AbstractColumn{Type,Value} classes
changed XXXColumnValue classes -- fixed set methods
changed ColumnType class -- uses BooleanColumn{Type,Value} objects
updated td-import.jar
added new feature to 'mysql' table reader: it can translate values of datetime type into unix times of long type automatically
changed CHANGES.txt