Rename server.py into dpserver and use rc.py

Objective
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- unify excutable name into `dp*`
- use new command-line interface introduced in `dpmanip`

Summary
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- introduce another configure loader in which configure is loaded into argparser instance
- rename `server.py` into `dpserver`
- change CLI of `dpserver`

PR status
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- related to #125 
Please add `nargs`.
Its value makes zsh completion more intelligent.