Add org.joda.time.chrono to exports
Merge pull request #948 from itheiss/master

org.openhab.core.persistence/META-INF/MANIFEST.MF: Add org.joda.time.chrono to exports
Update README.md
Added "synchronized" keyword to prevent race condition in RRD4JService.store() function. This race condition caused spurious
data to enter the rrd4j persistence files, resulting in spikes in charts.
Merge pull request #952 from berndpfrommer/master

added "synchronized" keyword to prevent race condition in RRD4JService