Quick fix - added default constructor to VKSource

Enabled debug mode for Picasso lib - to catch bug.
Fixed proper attachments display by hack (need to look into it to completely solve recycling problem)

Implemented loading of next elements

TODO:

HIGH PRIORITY:
- Loading of next/previous elements after screen rotation
- Detailed post view
- Parse and display copy_history field (array)
- Properly display date

LOW PRIORITY:

- Look into recycling View in adapter bug to avoid fix by hack