Precompute all values of 10^n. This consume 5 kb of memory, but simplify the code and guaranteed performance.
The performance issue was not a concern for fractionDigitsForDelta and fractionDigitsForValue, because those
methods are invoked only once for a dataset. But performance become more an issue for floatToDouble and the
upcomming method for completing the error term in double-double arithmetic (to be committed later), since
those methods will be invoked for all data values instead than for the dataset.


git-svn-id: https://svn.apache.org/repos/asf/sis/branches/JDK7@1538605 13f79535-47bb-0310-9956-ffa450edef68