Merge pull request #650 from sbesson/rebased/dev_4_4/findbugs-fix

Java 1.7/Findbugs fixes (rebased onto dev_4_4)
merge dev_4_4 -D org -I include -E exclude: PR 622 (Upgrade SLF4J to 1.7.2 [dev_4_4])
merge dev_4_4 -D org -I include -E exclude: PR 653 (Make JDK 1.6 the minimum supported version (dev_4_4))