Subsurface 4.5.6 released

Tue Apr 26 10:14:20 PDT 2016

Haven't written the announcement, yet.

 Some of the changes since _Subsurface_ 4.5.5                                                                                                                                                                                               
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 - Fix crash when downloading from Bluetooth based dive computers
 - Small fixes to VPM-B ceiling calculations
 - Import picture URLs from divelogs.de
 - Add support for the new version of the Suunto DX
 - Don't get caught in endless loop of git authentication errors
 - Fix time parsing of Divesoft Freedom
 - Support DAN DL7 import