Version 1.2.0

• Chg #319: Remove use of abstract type SchemaInterface::TYPE_JSONB (@Tigrov)
• Enh #300: Refactor ArrayExpressionBuilder (@Tigrov)
• Enh #301: Refactor JsonExpressionBuilder (@Tigrov)
• Enh #302: Refactor ColumnSchema (@Tigrov)
• Enh #321: Move methods from Command to AbstractPdoCommand class (@Tigrov)
• Bug #302: Fix incorrect convert string value for BIT type (@Tigrov)
• Bug #309: Fix retrieving sequence name from default value (@Tigrov)
• Bug #313: Refactor DMLQueryBuilder, related with yiisoft/db#746 (@Tigrov)