v5.1.5.RELEASE

Change log:

a578cee (5.1.x) Upgrade dependencies; prepate for release
0492889 Fix MessagingGatewaySupport implementors
bcf5929 Synchronize RemoteFileUtils.makeDirectories()
e465a9b GH-2901: Add missed delegates into JmsInGateway (#2903)
66c45e5 Downgrade H2 to 1.4.197
0b82222 Clean up more schema before JDBC tests
8219aba Drop H2 schema before JDBC tests
ad8d836 Fix race condition around sharedJschSession
bfebbbb GH-2884: RedisUtils improvements