[DBClientAction] Add a workaround for broken isIncidentSenderEnabled()

It always returns false when the first action in DB is invalid
(the corresponding incident tracker doesn't exist).

The root cause is the validator in getActionList(). It may drop
fetched records, so it conflicts with "LIMIT" clause of SQL.
We should fix getActionList() side to resolve this issue completely.
Merge pull request #351 from project-hatohol/workaround-checking-active-issue-sender

[DBClientAction] Add a workaround for broken isIncidentSenderEnabled()
[SQLUtils] Remove an unused method: createItemData.
[travis] Fix text

Fixes #352
Merge pull request #353 from project-hatohol/fix-travis-test

[travis] Fix text
Merge pull request #354 from project-hatohol/remove-create-item-data

[SQLUtils] Remove an unused method: createItemData.
[server] Use "Impl" and "m_impl" for PImpl idiom code

We used "PrivateContext" and "m_ctx" for PImpl idiom code.
"Impl" and "m_impl" are more readable name for PImpl idiom code rather
than "PrivateContext" and "m_ctx".
[server] Use std::unique_ptr or std::auto_ptr for Impl

I didn't test with "configure --enable-cpp11". Sorry.