Fix the build on Windows

Do not use ENGINIOCLIENT_EXPORT in plugin code
since it messes up the build on Windows.
Add missing export for EnginioFakeReply since
the symbol is needed by the plugin.
Fix the out-of-the-box experience for QtQuick examples on Windows

On Windows the binaries are produced into the release/debug subfolder
so we need to adjust the QML import path additionally.
Also remove extra main.cpp and use the shared one with the todos example.
Merge pull request #167 from bbandix/windowsFixes

Windows fixes