v1.7.15.RELEASE

Change log:

ef72f80 Upgrade Spring Version; prepare for final release
d4b7578 GH-1236: Handle non-String contentType
efcba3a GH-1237: RCFB Close key/trust store input streams
028b28a GH-1225: Fix Log4j2 Appender Termination
11c4367 Fix another exchange declaration
1eb4b35 Fix test exchange declaration
eeaeb68 Fix Appender Test
304832d Remove unnecessary slf4j dependency
3b96745 Artifactory compatibility: Gradle to 4.10.2
16a87df GH-1219: Fix header mapping for replies (@sendto)
c1566ff Make sendTo.replies test queue args consistent