Added abstract shell surface
Moved xdg_surface to abstract shell surface
Moved shell_surface to abstract shell surface
Used the correct buffer in ws_frame_buffer
Used ws_buffer_data instead of accessing it directly in ws_cursor
Removed buffer member from ws_raw_buffer
Fix cleaner iteration
Merge pull request #524 from TheNeikos/add-base_shell_surface

Add base shell surface
Merge pull request #525 from TheNeikos/fix-image_data

Fix image data
Merge pull request #527 from matthiasbeyer/fix-cleaner

Fix cleaner iteration