Fix formatting in build.gradle.

Replaced extra leading spaces with tabs.
Reinstate "launch" task as alias for xd-dirt:run

Added a launch task which explicitly depends on the spring-xd-dirt:run task to avoid confusion due to project ordering etc.
XD-139

Fix gradle build scripts to add appropriate task dependency for the bundle task
Update README doc with improved steps detail
Merge remote-tracking branch 'springsource/master' into xd-139

Conflicts:
	build.gradle
XD-139 Merge pull request #19 from ilayaperumalg/xd-139