column,table实体添加注释属性 (#24)

column.go

@@ -37,6 +37,7 @@ type Column struct {
 	SetOptions      map[string]int
 	DisableTimeZone bool
 	TimeZone        *time.Location // column specified time zone
+	Comment         string
 }
 
 func NewColumn(name, fieldName string, sqlType SQLType, len1, len2 int, nullable bool) *Column {
@@ -60,6 +61,7 @@ func NewColumn(name, fieldName string, sqlType SQLType, len1, len2 int, nullable
 		IsVersion:       false,
 		DefaultIsEmpty:  false,
 		EnumOptions:     make(map[string]int),
+		Comment:         "",
 	}
 }
 

table.go

@@ -22,6 +22,7 @@ type Table struct {
 	Cacher        Cacher
 	StoreEngine   string
 	Charset       string
+	Comment       string
 }
 
 func (table *Table) Columns() []*Column {