test/encoding/readable.sh: add non-whole type skip

test/encoding/readable.sh: add non-whole type skip

With this modification there will be possibility to skip only one/few
object/s of particular type, not whole type as it was before.

Before:
- To skip whole TYPE create file named TYPE in forward_incompat
directory.

Now:
- To skip whole TYPE create file or empty directory named TYPE in
forward_incompat directory.
- To skip one/few object/s of TYPE create directory named TYPE in
forward_incompat and put into symbolic links to objects that
you wantt to skip.

Signed-off-by: Igor Podoski <igor.podoski@ts.fujitsu.com>