refactored int codecs to DRY and easy support signed/unsigned values

src/commonMain/kotlin/net.sergeych.bintools/DataSink.kt

@@ -1,8 +1,8 @@
 package net.sergeych.bintools
 
-abstract class DataSink {
+interface DataSink {
 
-    abstract fun writeByte(data: Byte)
+    fun writeByte(data: Byte)
 
     fun writeByte(data: Int) = writeByte(data.toByte())
 
@@ -16,7 +16,7 @@ abstract class DataSink {
     }
 }
 
-class ArrayDataSink : DataSink() {
+class ArrayDataSink : DataSink {
     private val result = mutableListOf<Byte>()
 
     override fun writeByte(data: Byte) {