XD-591 Improve build file distribution tasks

Making distZip copy all binary installs into the primary distribution
zip file. This was previously done in zipXD

Making distZip part of Application tasks - overriding description
from application plug-in

Adding distTar as part of Application tasks - overriding description
from application plug-in

Renaming distXD to copyInstall for consistency and making it part of
Application tasks

Changing description of dist, keeping it as the the driving task for
generating all distribution artifacts to be consistent with the build
for Spring Integration
XD-591 Updating README for distribution zip
XD-576-2 Refactor Target Handling in Shell

* Put URL of admin server into the banner
* Add error messages to banner IF targeting was unsuccessful
* Add a new class `Target` which encapsulates Target URI, error/success state+messages

XD-576-2 Code Review - remove super() from Target