Implement ServerPort portion of wst.servertools API

WTP has support for port monitoring in it. This is a piece of code that I've neglected to implement for, oh, 9 years. I think now's the time, since bbrodt_jira has been asking about it.

Unfortunately, I've been hit by an upstream bug that hinders my progress:

https://bugs.eclipse.org/bugs/show_bug.cgi?id=466109

To be clear, I have a proposed patch which works for HTTP monitoring but simply doesn't function for monitoring the management port due to an upstream bug.