Fix typo in javadoc

(Cherry picked from commit bebbe92)
Fixes gh-1633
Exclude log4j:log4j in favor of org.slf4j:log4j-over-slf4j

Closes gh-1660
Merge branch '1.1.x'
Fix typo: InMemoryMessageRespository -> InMemoryMessageRepository

Closes gh-1671
Merge branch '1.1.x'
Fix the rest of the typo InMemoryRepository's name
Merge branch '1.1.x'
Add a logging system, starter and sample for Log4j 2

Closes gh-1565
Add HealthIndicator that checks free disk space

See gh-1297
Polish disk space health indicator

 - Supply auto-configuration for the new indicator
 - As suggested in the pull request, include the free disk space and
   configured threshold in the health details
 - Update the documentation to describe the indicator and its
   two configuration settings
 - Use @ConfigurationProperties to bind the indicator's configuration.
   This should make the changes sympathetic to the work being done
   to automate the configuration properties documentation

Closes gh-1297
Merge branch 'disk-space-health-indicator'
Fix tests after addition of disk space health indicator
Fix Actuator sample's health test
Polish
Add ActiveMQ MQTT connection URL auto-detection

Fixes gh-1638
Merge pull request #1638 from hekonsek/spring-boot-amq-mqtt

* spring-boot-amq-mqtt:
  Add ActiveMQ MQTT connection URL auto-detection
Support Jetty HandlerCollection types

Update JettyEmbeddedServletContainer to support HandlerCollection types
in addition to HandlerWrappers.

Fixes gh-545
Closes gh-1597
Merge pull request #1597 from liujiong1982/spring-boot-545

* spring-boot-545:
  Support Jetty HandlerCollection types
Add CAMELCASE_TO_HYPHEN in RelaxedNames

Fixes gh-1499
Merge pull request #1499 from liujiong1982/spring-boot-1499

* spring-boot-1499:
  Add CAMELCASE_TO_HYPHEN in RelaxedNames