Incorrect format with ExponentialDatumFormatter at resolution limits

[jbfaden]

Masafumi pointed out the issue when zooming in on an axis. This Jython code shows the root of the problem:

from org.das2.datum.format import ExponentialDatumFormatter
format= ExponentialDatumFormatter(20,7)

print format.format(datum(4.28230E7),Units.dimensionless)  # 0.0922337203685477500E7

[jbfaden]

I catch case Masafumi saw, where excessive resolution (20 decimal places)
resulted in 0.0922337203685477500E7. This is when Math.round(4.282336119000001*(10**20)) results in Long.MAX_VALUE. There is still an issue as to why it thinks it needs so many decimal places.