[Dextrose] Backport bugfixes from 0.90/master

[Aleksey Lim]

I've reviewed commits to the sugar master repo and picked up some
bugfixes that might be useful to include to dextrose-2. All of them
are fixes, some a useful and not invasive, some migth be considered
important/critical.

[PATCH sugar 01/11] Add missing import in jarabe.model.network (#2106)
[PATCH sugar 02/11] Sugar gconf settings breaks mouse buttons behaviour in gnome session #1544
[PATCH sugar 03/11] Journal:show error message on write failure: #1842
[PATCH sugar 04/11] Journal: Alert if an error occures when copying to devices in the detail view #1842
[PATCH sugar 05/11] Fix typo
[PATCH sugar 06/11] Remove separator in Journal toolbar #2446 (Gary C. Martin)
[PATCH sugar 07/11] Journal list view: don't choke on invalid or incomplete metadata (SL#1408)
[PATCH sugar 08/11] Journal details view: don't choke on invalid timestamp (SL#1590, SL#2208)
[PATCH sugar 09/11] datastore.write expects a DSObject, not an id
[PATCH sugar 10/11] Fix more sugar.datastore breakage
[PATCH sugar 11/11] fix journal scan of external media, dev.laptop.org #10140