[HatoholArmPluginStandard] Plug a memory leak
Merge pull request #772 from project-hatohol/plug-memory-leak-arm-zabbix

[HatoholArmPluginStandard] Plug a memory leak
[Params] Define HostIdSet.
[DBTablesHost] Implement getVirtualMachines().
[DBTablesHost] Use tableProfileHostHostgroup for checking host access.
[DBTablesTest] Use the new host tables.

I will squash this commit in the clean up later.
[DBTablesTest] Add test data.
[testDBTablesHost] Clean up a test for getVirtualMachines().
Merge pull request #774 from project-hatohol/add-graph-page-3

Initial implementation of drawing graphs
Merge pull request #777 from project-hatohol/host-management-4c

Host management 4c
[HistoryView] Discard raw history data immediately

Meaning data is stored in self.plotData so the raw data isn't
needed.