Drop using symlinks for documentation markup rendering

Drop using symlinks for documentation markup rendering

Keeping only symlinks as the markup indicator does not trigger CI on
relevant patches changing documentation contents (there's no change in
symlink).

This can be resolved by dropping symlinks usage entirely. Sphinx and RTD
aren't going anywhere anytime soon.

To make sure all symlinks were replaced following one-liner was used:

$ find . -type l -name "*.rst" -exec readlink -e {} \; \
  | xargs -I% git mv -f %{,.rst}

which finds all the symlinks in the repo with "*.rst" suffix, then reads
which file they link to and finally replaces given symlink with that
file.

This solution was suggested by:
Bartek Grzybowski <b.grzybowski@partner.samsung.com>

Issue-ID: INT-1672
Change-Id: I120e216b0b48032bb7b80c23cad799cd6f7cca53
Signed-off-by: Pawel Wieczorek <p.wieczorek2@samsung.com>