bnc#580834: HTML import: Embed images if source URL is a local file.

Use also INET_PROT_FILE to determine whether to import images as links.

(cherry picked from commits 3914a711060341345f15b83656457f90095f32d6
and 72703173066a2db5c977d422ace59d60b998bbfc and
38faee21e0b874359246e513b0a8c0af399a864d)

Conflicts:
	sw/source/filter/html/htmlgrin.cxx

Change-Id: I22a5ded92d9aac4220c0c4fa8bb8a9490f5c61a6
Reviewed-on: https://gerrit.libreoffice.org/11542
Reviewed-by: Andras Timar <andras.timar@collabora.com>
Tested-by: Andras Timar <andras.timar@collabora.com>