[Vim-l] Tip imports and navigation

[John Beckett]

After the initial import, there were a number of problems concerning invalid
VimTip links (illegal titles), and tips that failed to import, and other
drama. I think that all these problems are now fixed - let me know if you
see any bugs.

You might want to check some of my recent changes:
- All missing tips have been imported.
- No tips have titles with invalid characters.
- Tip navigation takes optional previous/next ids
  (see http://vim.wikia.com/wiki/VimTip1413 for a demo).
- There is a bullet between 'Previous tip' and 'Next tip'.
- On tip 1, 'Previous tip' goes to tip 1504.
- On tip 1504, 'Next tip' goes to tip 1.
- All VimTip redirects now point to a valid tip.
- Some VimTip pages use the new templates:
    Removed (tips we have deleted)
    OriginalDuplicate (tips duplicated on vim.org)
    OriginalMissing (tips not on vim.org)

See the following categories for examples:
  http://vim.wikia.com/wiki/Category:Removed
  http://vim.wikia.com/wiki/Category:OriginalDuplicate
  http://vim.wikia.com/wiki/Category:OriginalMissing

I have verified that all the tips in OriginalMissing really do not exist on
vim.org.

In due course, I will modify each tip (where required) so the previous and
next tip links point to a valid tip (currently, a link might point to a
Removed or OriginalDuplicate or OriginalMissing).

John