[bardesss]

Fixes from device testing and the remaining minor review items.

• Rows opened in a new list no longer turn read by themselves. The seen tracker kept time on screen per item id and only reset when the new snapshot was written, so items shared by the old and new list (say "All unread" and one feed) carried their dwell over and were marked while the new list jumped into place. Frames now carry the row list they were drawn from, and the tracker starts over on the first frame of a different list.
• SVG favicons load (coil-svg). The server passes a site's icon on as it is, and many sites only have an svg.
• A capped fetch is reported by refresh, so the new items pill no longer offers a refresh that cannot bring anything.
• A mark-all that stays queued shows "Some read marks could not be sent".
• A 403 is its own error and no longer signs out; only a 401 does.
• UnknownServiceException on an https address reads as unreachable, not as "needs https".
• Signing in with no recorded account wipes leftover local data first.
• JSON decoding runs off the main thread.
• The two-choice settings rows stack their segments under the label when they do not fit at large font sizes.

Tests: new ListViewModel, FaviconCache, SyncEngine, GReaderApi, sign out and settings layout tests. testDebugUnitTest, lintDebug and assembleRelease pass locally.