DbMonitorTest: simplified, using setup() method, when/then, etc.
DbMonitorPage: added methods: getCount (private), getActive, getMissing,
getAlert, getJoining; isServerListOpen, openServerList, closeServerList;
getServerNames, getMemoryUsages, getMemoryUsagePercents, getMemoryUsage,
getMemoryUsagePercent.
SchemaPage: just added slightly to 'at' list.
SqlQueryPage: just added slightly to 'at' list.
VoltDbManagementCenterPage: just added printDebug method; and minor
tweaks (like improving comments & deleting obsolete commented-out
lines).
DbMonitorTest: added new test methods: checkActiveMissingJoining,
openAndCloseServerList, triggerAlert, checkServerNamesAndMemoryUsage
(the last two need some more work).