Revert "introduced test.config for XMPP connection"

This reverts commit 12fc18874a47fae8b6da30a8bdf887120b1dc340.

use the fixed server settings
 * localhost/5222
 * auction-item-54321 for server id
 * bidder-1 and bidder-2 for bidders' ids
deleted MainWindowTest.java (has no tests)
removed time stamp from build init target