This commit is mainly intended to prevent the sort of false positives that occur when the upgrader assumes the server has been upgraded properly but leaves the server in a corrupt state (see issues 1546 and 1559).  The following changes are introduced:

- An additional stipulation is put on successful completion of the upgrade process:  early on in the process the server is started to see if it logs and severe messages upon startup.  If there are any severe messages the upgrade tool won't run.  Later when the upgraded server is being verified, the messages are checked again to see if there are any severe messages.  If so the upgrade is aborted and any changes are backed out.  The error message are returned from startServer methods in a new class OperationOutput. 

- The upgrade tool no longer allows a reversion to an older version and now checks to make sure the current version is older than the proposed version by comparing the major, minor, point, and SVN revision numbers obtained by running start-ds -F and storing the values in a new class BuildInformation.

- The choose version screen now takes web proxy host and port from that standard system properties if they are set.