[Core] Avoid trying to load non-exec files in $PWD.
[Azoth Xoox] ClientConnection::GetErrorManager().
[Azoth Xoox] More AdHocNote ctors.
[Azoth Xoox] ClientConnectionErrorMgr::SetErrorHandler().
[Azoth Xoox] Register error handler in ad-hoc mgr for #1766.
[Azoth Xoox] Return the request ID from ad-hoc mgr.
[Azoth Xoox] Slight ExecuteCommandDialog ctor refactoring.

Moved common stuff into a base tagged ctor to be invoked by delegating.
[Azoth Xoox] Handle ad-hoc manager errors, finally fixes #1766.