Do not print useless digits when displaying file size
The original implementation (using FileUtils) was truncating every numbers. We had remarks from end users that printing 1Gb when the file has in fact a size of around 1.92 Gb is considered as wrong. This was solved by issue #2 (closed).
However, printing that a file size is 1.00 Kb when in weights exactly 1024 bytes is not satisfying.
The idea is to rely on decimal formatter that is itself able to print a maximum the number of significant digit and truncate before if useless.
The idea is to still have 1.92 Gb, but 1 Kb only.