Add project pipe

Objective
------------
I hope the following command works.
```command
dpmanip -s add_project . project1
```
It is important to specify a project by its name not by path.

Summary
------------
- introduce `rc.get_project_dir` to generate path from name
- introduce `add_project` pipe

The directory in which the project directory will be created is specified by the setting file (`~/.dataprocessor.ini`),
and thus `get_project_dir` is included in `rc`.