Add the DataInput / DataOutput interfaces

These are part of the standard Java class library API.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Add a minimal implementation of DataOutputStream

This implements all the methods required by the DataOutput interface; to
run Bio-Formats' bfconvert tool, actually only the write() and writeByte()
methods would be required.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Merge pull request #86 from dscho/data-output-stream

Data output stream