A paper correspond to 3 files :
    name.pdf              a pdf or ps file, the paper itself, whose location is arbitrary
    bibdata/name.bibyaml  a bibyaml file with all bibliographic data.
    meta/name.meta        a metadata file for internal use, notes, citekeys, status, etc.

+ requires config file (default repo, open command, ...)
- printing should include templating engine and several templates for bib types and output
  * chose existing engine
- tests...
- import command for interactive import with auto bib
  * basic title and author search in pdf
  * online services (scholar, etc.)
- add command does not require pdf -> add from bib

About strings:
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- pybtex seems to store entries as utf-8 (TODO: check)
- so assumption is made that everything is utf-8
- conversions are performed at print time

Config values:
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[papers]
open-cmd = open
edit-cmd = edit
import-copy = True
import-move = False
terminal-encoding = from locale or utf8