Lazy load cached data - need to not load all data up front

[smalers]

Quite a bit of data are loaded up front in order to create a cached time series catalog. This slows down startup and puts a load on the Zabbix server every time TSTool is run. An alternative is to do lazy loading and only load global data if Zabbix features are actually used. This would involve calling the readGlobalData code only when needed. The problem is that some components such as UI input filters, get populated up front, so would need to figure out how to set up the UI skeleton and then populate later.