Server Monitoring and Resource Utilisation

The eeePC ran out of HDD space, resulting in shut down of Sahana server until we cleared out HDD space and reinitialized.

We would like to add a server monitoring function - linked to in About Sahana - and maybe in Admin module as well - that would display vital stats about the server - including HDD space remaining. Need to define capacity and limits (probably in %) that we want warning messages to be sent (possibly via SMS or e-mail) - but for now - let's start with a simple monitor.