SrmDevice: fix writing srmio data

fopen() was missing 'b' flag, so that mingw and other platforms doing
LF/CR translation screwed data.

This is fixing the astronomic values of direct SRM downloads.
inlude srmio version + commit in about dialog
Fixup Fit File issue

Fixes #646

- not cherry picked from master because there is a small
  update in the patch related to a 3.1 development.