[ItemFetchWoker] Make a DataStore instance fetch items on demand.

Previously fetching items was in charged of ArmBase. However,
HatoholArmPluginGate is not a sub class of it. And I'm thinkg that
ArmBase should be removed (deprecated) because it was designed for
the conventional Arms such as ArmZabbixAPI and ArmNagiosNDOUtils.

So this patch suggests that a DataStore instance performs the task
instead of ArmBase.
[Monitoring.h] Fix an indent.
[HatoholArmPluginGate] Add basic framework to get fetch items on demand.
[HatoholDBUtils] Fix a typo of the variable name.
[CommandCallbacks] Remove 'const' from replyBuf.

Sometimes the callback want to change the index of the buffer.
However, const prevents it.
[HatoholArmPluginInterface] Log an error of onReceived().
[Params] Add a new type.
[Params] Rename a type name to avoid confusion.

ItemgroupIdType ->
ItemCategoryIdType

ItemgroupId is similar to ItemGroup which is the internal data
structure. It will confuse developers.
[Param] Fix a typo.

FMT_ITEM_CATEGROY_ID ->
FMT_ITEM_CATEGORY_ID
[HatoholDBUtils] Change the variable name fashion.

Although the name 'ppplication' is derived from Zabbix, but it's
a little hard to understand what it means.
So we use 'ItemCategory' for them.
[HatoholDBUtils] Accept items without the item category.
[HatoholArmPluginInterface] Set an index of the response buffer to improve convenience.
[Params] Move definition of ItemCategoryNameMap etc. to Params.h

The patch makes other classes can use it.
[HatoholArmPluginGate] Save the fetched Item in the DB.
[Params] Fix a build error on Ubuntu 12.04.
Merge pull request #640 from project-hatohol/hapi-get-item-on-demand

Hapi get item on demand