2154: Changed the way we determine if a language is a translation.

We used to be looking into the lineage, but that is a dict and choosing the first item could return the right version, or not ;). We're not using SubtitleVersion.parents as that makes it easier to ensure the 'latest' parent is always brought in.
Merge branch 'staging' into i-2154
2154: Removed unused variable
Merge branch 'staging' into i-2154
2154: fixed "translated from..." display.

Fixed to_localized_display to return the language name in the current
locale, instead of the locale of the language.

Rewrote the translation block to use blocktrans instead of multiple
trans lines.
2154: remove the start subtitle warning message

The message was pretty messed up for various reasons:
  - The check for when we should show it was wrong
    (unisubs.startdialog.Dialog.FORK_VALUE doesn't seem to be used
    anywmore)
  - The warning that we should show it from scratch was incorrect, we
    don't need to start from scratch anymore.

  - The warning that there are better choices for the from languages
    crashed and prevented the warning from being shown.  We could fix
    this code, but I don't think the check is correct in any case.

Let's just remove this code.  If we need to add something back, then
it's easy to do.
2373: Mark language as fork on the old dialog if any subs have been added or deleted. This should make the backend work as is, but we should watch out for unexpected changes
Merge branch 'staging' into i-2154
2374: fork dependent translations on upload
Merge branch 'i-2373' into i-2374
Merge branch 'staging' into i-2374
2374: move forking during uploads to the pipeline
2374: allow uploading to languages with dependents
2374: fix tests to allow uploads to parent languages
2373 Forks immediate dependents on the widget too if the dialog tells us to fork
Merge branch 'i-2374' into staging