Do not change link text on file move/rename

[Zauber Paracelsus]

When moving or renaming a page in Zim, you are given the option to update the links to the page. But quite often, if the "link to" and "text" parts of a link (as shown in the Edit Link window) are the same, then both are changed. This can be annoying, as it makes it much more difficult to update links when you do not want the page text to be changed. There should be an option to block this behavior, so that there is no change to the link's displayed text, only to the link itself.