XD-538 - Develop infrastructure to enable testability of commands

* Add code to cleanly shutdown tomcat as taken from Tomcat unit tests - not used as still hangs on tomcat.stop()
* Force shutdown of tomcat using destroy method, log warning.
* When random port is requested, retrieve port that was selected by the system
* Destory web application contex in StreamServer stop to avoid reflection calls from clients of StreamServer that want to stop the server cleanly
* XDShell processes command line arguments --port and --host to configuration how to connect to XDAdmin on startup
* XDShell target command will throw an exception to indicate failure of the command.
* JobCommands and TapCommands return Table objectd for list command
* Update ReferenceDoc command that uses shell to take into account CommandLine class that is autowired
XD-538 - Develop infrastructure to enable testability of commands

* Add code to cleanly shutdown tomcat as taken from Tomcat unit tests - not used as still hangs on tomcat.stop()
* Force shutdown of tomcat using destroy method, log warning.
* When random port is requested, retrieve port that was selected by the system
* Destory web application contex in StreamServer stop to avoid reflection calls from clients of StreamServer that want to stop the server cleanly
* XDShell processes command line arguments --port and --host to configuration how to connect to XDAdmin on startup
* XDShell target command will throw an exception to indicate failure of the command.
* JobCommands and TapCommands return Table objectd for list command
* Update ReferenceDoc command that uses shell to take into account CommandLine class that is autowired

Merge remote-tracking branch 'upstream/master'

Conflicts:
	spring-xd-dirt/src/main/java/org/springframework/xd/dirt/server/AdminMain.java