[server][DBClientConfig] Add a new method: getServerIdSet().
[server][DBClientConfig] Clean up by using a common helper function.
[server][DBClientConfig] Replace a raw type: uint64_t with an abstract type.
[server] Fix a wrong name by mistake.

ServerIdSetIterator ->
ServerIdSetConstIterator
[server]DBClientHatohol] Add a new method: HostResourceQueryOption::makeConditionServer().
[server][DBClientConfig] Use const & for an input paramter.
[server][DBClientConfig] Add a new constructor of ServerQueryOption.
[server][testDBClientConfig] Add a missing setup.
[server][DBClientHatohol] Use const & for an input paramter.
[server][DBClientHatohol] Add a missing 'IN' operator.
[server][DBClientHatohol] Make a space to be the same as other statements with 'IN'.
[doc] Add a README.
[doc] Fix doxygen.conf for the current source code placement.
[doc] Update doxygen.conf.

This patch is to suppress the following warning on Xubuntu 13.10.

---
$ doxygen -u doxygen.conf
Warning: Tag `SYMBOL_CACHE_SIZE' at line 336 of file doxygen.conf has become obsolete.
To avoid this warning please remove this line from your configuration file or upgrade it using "doxygen -u"
---

According to the message, I did the following command.

    $ doxygen -u doxygen.conf
[doc] Revised a statement of README.
[server] Rename ItemPtr to UsedCountablePtr.

The reasons are the following.
- It is not only for ItemData, ItemGroup, and ItemTable.
- It can be used for any classes that inherits UsedCountable.
[server][test] Rename a test name.

testItemPtr ->
testItemDataPtr

The test is for ItemDataPtr, not for ItemPtr (currently UsedCountablePtr).
The previous name is unsuitable.
[server][DataQueryContext] Add a new class.
[server][DataQueryContext] Add a new method: getServerHostGrpSetMap().
[server] Move some definitions to Params.h to fix a complicated dependency of headers.

Especially, I didn't want to include DBClientUser.h in DataQueryContext.h