added TableColumnFragment
added TableColumnNotNullConstraint
added LiteralTableColumnDefault
added ConstantTableColumnDefault
added PrimaryKeyConstraint
added UniqueConstraint
added ForeignKeyConstraint and fixed register* methods, some constnes
fixes
started to work on sql abstraction library
added Command and Comment
added comments to commands
added support for multi row comments
added transaction commands
moved transaction commands to their own directory
started to work on query framework
added CreateSchema
can drop database schema using model
started to work on database object create script