portal pieces: rename files according to item naming scheme

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

diff --git a/library/edited/portal-blue-black.svg b/library/edited/b-portal-blue.svg
similarity index 100%
rename from library/edited/portal-blue-black.svg
rename to library/edited/b-portal-blue.svg

diff --git a/library/edited/portal-orange-black.svg b/library/edited/b-portal-orange.svg
similarity index 100%
rename from library/edited/portal-orange-black.svg
rename to library/edited/b-portal-orange.svg

diff --git a/library/edited/portal-blue-white.svg b/library/edited/w-portal-blue.svg
similarity index 100%
rename from library/edited/portal-blue-white.svg
rename to library/edited/w-portal-blue.svg

diff --git a/library/edited/portal-orange-white.svg b/library/edited/w-portal-orange.svg
similarity index 100%
rename from library/edited/portal-orange-white.svg
rename to library/edited/w-portal-orange.svg