Remove any empty label that the server sends, as we maintain out own empty label. Fixes #79.
Prepared for #7 auto refresh by adding a system setting (and moving help options to a separate screen).
Added auto refresh to the activity

OnResume creates an AsyncTask which keeps running
until cancelled. It requests server updates with
a delay of two seconds between each update.

OnPause cancels the AsyncTask.

To handle multiselect gracefully, the fragment requests
the auto refresh to be paused. This pause is remembered
between resets, as long as the multiselect mode is active.
Once the users selects an action or exits multiselect,
the auto refresh resumes.

There are probably several things I haven't thought of,
and there should be a user setting for this maybe.

Signed-off-by: Jonas Kalderstam <jonas@kalderstam.se>
Integrated the auto refresh timer with its setting after @spacecowboy merge, which fixes #7.