* Upgrades rrd4j to 3.8 * Fixes deprecations * Updates RRD4jChartServlet for ChartProvider API changes * Improves RRD4jChartServlet exception handling For the rrd4j changelog see: https://raw.githubusercontent.com/rrd4j/rrd4j/master/changelog.txt Related to openhab/openhab-core#2502 Signed-off-by: Wouter Born <github@maindrain.net>