We need to tell DT that we are adding/removing row, not only deal
manually with the DOM.
This patch also fixes the following bug: if you add or remove a row from
the "biblio" tab, then go to another tab and back to "biblio", all
changes were gone (bug existed prior to bug 29893).
Test plan:
Add, edit and remove mappings, switch from tabs and save.
Use the filters, save (29893 regression test)
Signed-off-by: David Nind <david@davidnind.com> Signed-off-by: Nick Clemens <nick@bywatersolutions.com> Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>