use begin() and end() when calling std::copy on an uno::Sequence

Inspired by commit b34b648f
"uno::Sequence provides now begin and end"

Change-Id: I08e8c3fd6144e77b95a26f85bc0daf6a9edeeb0b
Reviewed-on: https://gerrit.libreoffice.org/16057Reviewed-by: Noel Grandin <noelgrandin@gmail.com>
Tested-by: Noel Grandin <noelgrandin@gmail.com>