Initial code checkin

Very rough initial version that has necessary C# API bindings for
official GOG.com API, support API authorization flow. This would be
used for local files verification.

Additionally the app can download local data cache - dataCache.json
(and .js for easier browser consumption) and game product images. There
is initial html that can consume this and show on a single page,
supporting high-resolution assets on high DPI displays. There would be
detailed view as well as search, etc.