Separated client- and server-side features into seperate root folders. Since Stadia Avatar now has two versions (Userscript and Chrome extension).
Added core extension functionality.
Created a page constructor for extension popup. High probability that I will create a seperate repo for this feature, as it's pretty neat and very useful for future extensions.
Added new extension of DBConnector called StadiaAvatarDB. This class contains all avatar manipulation queries.
Fixed get and update.
Added Gravatar hash generator.
