Make org-velocity more useful for file navigation.

In particular, when `org-velocity' is called from inside an Org file, and it searches that file, instead of editing the entry in a separate buffer, edit it in the same buffer.
Simplify narrowing.
Only jump to the end when using capture.
Preserve text properties in previews.
Make more useful for navigation.
Dump the staging buffer.
Display a header with the file being searched.