Serialize Option[T] in DataSerializer

[aslesarenko]

Problem

DataSerializer is used to serialize data values for any supported ErgoTree type. It is in particular used to serialize Constant values, where type is first serialized (see TypeSerializer) and then the constant value is serialized using DataSerializer).
Option[T] is supported type of constant values, i.e. it is possible to create tree node like Constant(SOption(SInt), Some(10)), however DataSerializer don't support serialization of Option[T] values and hence such constants are not supported.

Solution

Add Option[T] case in DataSerializer using Writer.putOption method.

[kushti]

done in #990