Add extra views (tabs) for files in a foreign repository

Previously, foreign files with no local page had only a [Create] tab, with
no explanation that this created a local description page. There was not
even a [Read] tab - from SkinTemplate's perspective, a foreign file page
did not exist.

This patch changes the following view tabs:
* [Read] now always appears on foreign files - no change in functionality
* New tab [View on <repo name>] always appears on foreign files
* [Create] tab renamed to [Add local description] for foreign files without
  a local page
* [Edit] tab renamed to [Edit local description] for foreign files with a
  local page

This is related to bug 26525. I am hesitant to implement a [Edit on
<repo name>] tab that goes straight to the edit screen, as I worry about
users getting confused and thinking they are editing the file locally.

Change-Id: I4a43b759b7a7e9ac2c8d437408847bf3b6c1f4a9
Merge "Add extra views (tabs) for files in a foreign repository"