Added support for system monitoring using Ganglia

Added two services 'monitor' and 'monitoring_server'. The first
installed an Ganglia agent, which make the node monitorable. The
second install an Ganglia Web frontend to allow user to check
the metric of monitoring node(s).
Merge branch 'master' into AERIE
Added supporting for choosing EC2 region.

Now, we supported to create EC2 instance in non-default region.
Users can add an XML element called 'region' in node(s) to
specify the desired region to launch the instance(s).
Merge branch 'master' into AERIE
Speedup the migration a little