Code clean up

Cleaned up unnecessary spaces, replaced tabs with spaces and fixed line
terminators.
Better message on error

Changed message from "conecting" to "error" as in this case
communication was over and was an error.
Added error_icon.png and spinner.gif images

Added error_icon.png and spinner.gif images to not make it dependent of
Plone resources.
Merge pull request #2 from alecghica/master

Code clean up + updated error message
Merge pull request #3 from ichim-david/master

Optimize actions done in RosterView.