added missing accelerators for "Formatted display", "All sheets", "Find previous"
resolved ambiguous accelerator for "Find"/"Find next"

Change-Id: I732c311e4db705afff0d4bc69e6efa086eddad3a
Reviewed-on: https://gerrit.libreoffice.org/28060Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Adolfo Jayme Barrientos <fitojb@ubuntu.com>
Tested-by: Adolfo Jayme Barrientos <fitojb@ubuntu.com>