[HostResourceQueryOption] Fix confusing treatment of table name alias

There are few issues in the previous implementation:

* enableTableVariable() was defined as const member function but
  it modifies its contents.
* getCondition() had an arugument "varName" but it never be used.
* There were 2 functions for a same purpose:
  - setTableNameForServerId()
  - setTableVariableName()

Now I think HostResourceQueryOption shouldn't hold table name
and a flag like "useTableVariable" because caller of
DBClientHatohol::getEventInfoList() or DBClientHatohol::
getTriggerInfoList() doesn't want that the content of
HostResourceQueryOption is modified.
Merge pull request #144 from ashie/issue27-client-fix-confusing-table-alias

[HostResourceQueryOption] Fix confusing treatment of table name alias