ui: add datastore usages to dashboard

shows an overview over the datastores, including a small chart of the
past month and an estimation of when its full

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>

www/Makefile

@@ -18,6 +18,7 @@ JSSRC=							\
 	window/SyncJobEdit.js				\
 	window/ACLEdit.js				\
 	window/DataStoreEdit.js				\
+	dashboard/DataStoreStatistics.js		\
 	Utils.js					\
 	LoginView.js					\
 	VersionInfo.js					\