Added additional library preview triggers.

Library preview is now triggered after every 'add'-action.
Added grouping for communication items.

Libary communication items, like pubs, subs, services and actions are
now grouped.
Added functions group.

Function are also now grouped into functions_item.
Fixed ServiceServer/Client support.

Fixed service server and client support in Controller and PyBackend.
Changed generated callback suffix in Communications from '_cb' to
'_callback'.
More eye candy

Added new icon for function item and set former function item icon as
functions group item icon.