Issue #1234 - Remove CString from ShouldBlock(), IsElementHidden() declarations

Changed from CString to std::wstring in the following declarations:
- CAdblockPlusClient::IsElementHidden()
- CAdblockPlusClient::ShouldBlock()
- CAdblockPlusClient::m_cacheBlockedSources
- CPluginFilter::IsElementHidden()
- CPluginFilter::ShouldBlock()

The function bodies in CAdblockPlusClient have been converted away from CString,
although those in CPluginFilter have not.

--HG--
extra : rebase_source : e31a57d6d0be422c07daeebc0904c8c7cc8dc8b4
extra : amend_source : 506252b179ed070a96f8f1cd81d12b214ee20e20
Issue #1234 - remove CString from declarations representing domains.

Replaced CString with std::wstring in a number of declarations that represent
domains.
CPluginDebug::DebugResultBlocking, argument
CPluginDebug::DebugResultIgnoring, argument
CPluginDomTraverserBase::TraverseDocument, argument, argument
CPluginDomTraverserBase::TraverseSubdocument, argument
CPluginDomTraverserBase::m_domain
CPluginTabBase::m_documentDomain
CPluginTabBase::m_cacheDomain
CPluginTabBase::GetDocumentDomain, return value
CPluginTabBase::ClearFrameCache, return value
WBPassthruSink::GetContentType, argument

Changed function bodies only as expedient; some occurrence of CString remain.

Removed dead function IsValidDomain().