github/openhab issue #1013: When the value was an integer and the format was like "%.1f", an exception was thrown

Signed-off-by: Martin <martin+github@planet-renner.net>
github/openhab issue #1013: values like "10.0" did not work with integer formats like "%d"

Signed-off-by: Martin <martin+github@planet-renner.net>
Merge pull request #23 from planetrenner-martin/decimal-formatter

Flexible formatting of DecimalType