Added Preview plugin stub.
Added interface ITokenFilter.
Text filters now get a message id.
[Preview] Added class PreviewFilter.
[Preview] Added classes PreviewChatView and PreviewWindowObject.
[Preview] Added classes PreviewDB and PreviewStorage.
[Preview] Added class PreviewItem.
Fixed crash.
[Preview] JS code now can obtain images ids.
[Preview] Added images.
[Preview] Initial spinner and error thumbs.
[Preview] Initial image preview.
[Preview] Implemented storage layer.
Fixed deletion of messages.
Added Http plugin for Windows NSIS installation.
Merge branch 'preview-plugin' into http