reference classes, uno::Reference and rtl::Reference.

Specifically rename Is()->is() and Clear()->clear().

Change-Id: Icb7e05e2d09cb9977121508b837ba0961dabb4ae
Reviewed-on: https://gerrit.libreoffice.org/33576Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>