XD-1305 File Sink now supports configurable modes

Originally the file sink only supported the append mode.
Now supports APPEND, REPLACE, FAIL IGNORE
XD-1294 Update xd reactor dependency

- Move the reactor Environment bean definition out of module common context
- Remove the 'spring-xd-extension-reactor' runtime dependency from spring-xd-dirt
- Add back 'spring-xd-extension-reactor' runtime dependency to reactor-syslog module

Add reactorEnv bean to syslog module

- Add the reactor environment bean to the reactor-syslog source
module so that the reactor environment is only loaded when this
module is deployed.
XD-1316 UI:Fix E2E test warning
Update xd ui test task

 Rename ui test task to 'ui_test' so that gradle test won't
  call spring-xd-ui tests. To run the E2E tests, the ui_test
  task needs to be invoked explicitly.
 The 'ui_test' task will also build the UI and runs the unit tests
  as it depends on 'grunt_build'

 Once we have valid UI tests, we will rename the task ui_test to 'test'
  so that will run as a 'test' task.
XD-804 Added integration.support package to dirt and used in AbstractSingleNode...Tests

XD-804. Refactored SingleNodeTestSupport and SingleNodeApplication per review

XD-804 Renamed package integration.test and added module resource location support

XD-804 Updated javadocs and added moduleResourceLocation arguments to processing chain creation methods

Javadoc fixes + random ports
XD-1090: Add job restart command