Csv decoder (#1290)

* WIP: adding CSV decoder

* Adding CSV decoder

* Added CSV roundtrip

* Fixing from review

pkg/yqlib/decoder.go

@@ -15,6 +15,8 @@ const (
 	PropertiesInputFormat
 	Base64InputFormat
 	JsonInputFormat
+	CSVObjectInputFormat
+	TSVObjectInputFormat
 )
 
 type Decoder interface {
@@ -32,6 +34,10 @@ func InputFormatFromString(format string) (InputFormat, error) {
 		return PropertiesInputFormat, nil
 	case "json", "ndjson", "j":
 		return JsonInputFormat, nil
+	case "csv", "c":
+		return CSVObjectInputFormat, nil
+	case "tsv", "t":
+		return TSVObjectInputFormat, nil
 	default:
 		return 0, fmt.Errorf("unknown format '%v' please use [yaml|xml|props]", format)
 	}