Disregard methods beginning with write when checking for mutability of a class

[baloghadamsoftware]

Methods beginning with write are almost always output methods (e.g. to streams) and no setters. Disregard them when deciding about mutability of a class.

Partial fix for issue [#1601](https://github.com/spotbugs/spotbugs/issues/1601\)

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[ThrawnCA]

IMO writing to a stream qualifies as changing its state. Especially with classes like ByteArrayOutputStream.

[baloghadamsoftware]

IMO writing to a stream qualifies as changing its state. Especially with classes like ByteArrayOutputStream.

You are right. However, if a non-stream class contains a method beginning with write it usually does not change the class but writes its contents into a stream.

[rovarga]

I think the signal-to-noise ratio for write*(...) is way too high. In its current form it trips on anything java.io.Externalizable, as well as anything using writeReplace() to implement Serializable Proxy pattern -- suppressing that is quite a bit of work, too, see #1704 .