Fix relative paths for VimwikiRenameLink. Merge PR #787.

Fixes #90 

__Problem__: VimwikiRenameLink does not rename dir1/toto url in dir2/tata
because the dirs (dir2 and .) were well crossed but badly inspected.
__Solution__: `blob(.ext*)` -> `glob(**/*.ext)` + find the relative URL

* Fasten: VimwikiRenameLink goes faster with cache
More: To compute old_url regex, use a cache dict because it is the same
for files in the same directories

* Util DeleteHiddenBuffer -> do not delete Vader buffer

* Test: Prettify: Util: teardown delete defined function

* Remove unnecessary trailing spaces
Note: list_VimwikiReturn.vader has some necessary trailing spaces

test/vader_includes/vader_setup.vader

@@ -58,11 +58,14 @@ Before (Define functions):
   " Delete Hidden buffer, usefull to clean
   " Stole from: https://stackoverflow.com/a/8459043/2544873
   function! DeleteHiddenBuffers()
-      let tpbl=[]
-      call map(range(1, tabpagenr('$')), 'extend(tpbl, tabpagebuflist(v:val))')
-      for buf in filter(range(1, bufnr('$')), 'bufexists(v:val) && index(tpbl, v:val)==-1')
-          silent execute 'bwipeout!' buf
-      endfor
+    let tpbl=[]
+    call map(range(1, tabpagenr('$')), 'extend(tpbl, tabpagebuflist(v:val))')
+    for buf in filter(range(1, bufnr('$')), 'bufexists(v:val) && index(tpbl, v:val)==-1')
+      if bufname(buf) =~ 'Vader'
+          continue
+      endif
+      silent execute 'bwipeout!' buf
+    endfor
   endfunction
 
   " Write current file: helper to hide `set bt=`

test/vader_includes/vader_teardown.vader

@@ -1,3 +1,6 @@
 After (Cleanup):
   delfunction SetSyntax
   delfunction ReloadVimwiki
+  delfunction DeleteHiddenBuffers
+  delfunction WriteMe
+  delfunction PrintCommand