Store Geiger log data in a Backbone collection:
we now save all the data on the browser's storage: this way when
the application starts, all previous data is restored, and new log data
is added to the existing dataset.
Fix on Firefox and other improvements.

Fixed bad init code on Firefox that prevented the app from working on
that browser. Now display a "Downloading..." prompt when downloading
data from the device. And also now stores all data in the browser's local
storage properly. New data does not overwrite old data. Clearing the counter's
memory does not erase data already present in the application.

Start of a log save feature (in json for now), not complete.