Add Zsh completion

## Objective
- Enable zsh completion of executables `dpmanip`, `dataprocessor`, `genzshcomp` and `register_figure`.
  Since big refactaring of `server.py` is needed for its completion function, this is not implemented.
- Enable creation of zsh completion function at `zsh_completion` directory by following commands.

```sh
genzshcomp dpmanip
genzshcomp dataprocessor
genzshcomp genzshcomp
genzshcomp register_figure
```

## Summary

- Separate creations of each executable argument parser to `lib/dataprocessor/dp_arg_parsers.py`.
- Add `bin/genzshcomp` and `lib/dataprocessor/gencompletion.py`
- Add zsh completion function.

## PR states

- related to #71 

## Notes

- Move zsh completion file to a directory included in `$FPATH` or add the directory `zsh_completions` to `$FPATH` for turning on completion.