add host to the cluster only if it is not expired
Fixes and simplications of build files.

Previously, Ganglia_statedir referred to /var/lib - not very specific to ganglia.
Also $GWEB_DWOO was defined, but not propagated to the conf template.

Now defined and propagated where appropriate:
 gmeta_rootdir (parent location of rrd folder)
 gdestdir (php files)
 gweb_statedir (parent of gweb 'conf' folder and 'dwoo' templates)

I've attempted to match up the RPM spec also, but I suspect that the
'custom_web_prefixdir' needs defining and passing from the Makefile.
Unfortunately I'm unfamiliar with RPM builds.
Merge pull request #147 from pcpiela/master

Minor updates
Merge pull request #146 from timstaley/fix-build

Fixes and simplications of build files.
Validate view names to make sure they are valid
Center cluster-view font for the stacked graph
Merge pull request #149 from seryl/center_stackedfont

Center cluster-view font for the stacked graph
Merge pull request #143 from miihael/master

Incorrect cluster name determined for the host
Incorporate the legend into into selection menu. Various cleanups.