This commit address issue 1674 <https://opends.dev.java.net/issues/show_bug.cgi?id=1674> to make the webstart and offline installers cancelable.  The plumbing for cancelability is already in place since the upgrader makes use of it.  This commit for the most part implements the actions that the installers must perform when the operation is canceled.

Note that I have not implemented steps necessary to unregister a server from replication but have left this as 'todo' for the time being.

For the Web Start installer:
- Stop the server if running.
- If the install has registered this application as a windows service unregister it.
- Delete the files that have been installed.

For the offline installer there are more steps since we can't just wipe out all the files:

- Stop the server if running.
- If the install has registered this application as a windows service unregister it.
- Revert the configuration to the base configuration.
- If SSL was configured delete the self-signed cert (if necessary), delete keystore, keystore.pin and truststore.
- Delete the database files.