Make sure using different server types with rse is somewhat predictable

I'm not sure how to approach this, but the main motivation for this JIRA is https://community.jboss.org/message/868575 .

Most often when I user rse servers, I select "ssh" as the host type when setting up the remote host. It's simply because I know this will work.

Currently there are plenty of types to choose from:

Some of them may work, others may not. I'm not sure how much control we have here, but we should try to ensure that there are reasonable warnings/errors or at least no NPEs when a user selects a type that does not really work.

For example I tried using FTP. I set up FTP on my server and created the remote server with that. Everything seemed fine until I tried to start the server. Obviously this will not work, but we should do better than throw a NPE. I intend to try each of the types and report back in the comments.

Feel free to push this JIRA further to a future release as necessary.