Update tagset

The tagset for annotations was updated. Most importantly the tag
levels changed. The kaf2folia script was updated to reflect these changes.
Fix adding entities to folia

Due to a bug in the code, only a single word of an entity was added to
the folia. This was fixed.
Improve readability of code

Small Improvement of readability.
Improve documentation

The kaf2folia script should only be used by the batch_add_tags.sh shell
script. This information was added to the documentation.
Add words to embodied emotions annotations

Folia allows the text content of words to be added to entities. Words
are now added to the entities that are inserted into the folia file.
This makes it easier to check whether entities were added correctly.
Prevent entity-annotation tag from being added multiple times

In the setup with the shell script, annotations are added in multiple
passes (one pass for each .tag-file). Because of this, an
entity-annotation tag was added in every pass. The code was changed to
only add the entity-annotation tag if it hasn't been added before.
Refactor batch_add_tags script

The batch_add_tags script now only adds tags to folia files for which
there are tag files, and not based on the availability of folia files
(as it was before).