#22 create converter wrappers around all immutables

[Mike J. Bell]

Each immutable needs a corresponding Converter
subclass which calls create() with the appropriate
arguments from supplied event channels. Example:

for ByteIlaFill, make ByteIlaFillConverter, which
takes triggering sinks ByteECD value and LongECD
length, and produces ByteIlaECD result as
ByteIlaFill.create(((Byte)get(value)).byteValue(),
((Long)get(length)).longValue())

Not sure where these should all be packaged. These
probably should be auto-generated from templates
along with the rest of the immutables.