Plugin include

Inclusion de fichier JSON contenant une liste de contenu.
Permet d'avoir le même contenu avec plusieurs mises en page.
Adds a warning message if _songbook_dir is not set
Gestion du cas où la clef _songbook_dir n'existe pas
Typo
Trying to solve encoding problems #50
Use datadirs as base search path for included content
Merge branch 'include' of github.com:patacrep/patacrep into include
Merge branch 'master' into include

Conflicts:
	patacrep/authors.py
Corrected indentation
Simplify case where datadir is empty
Guess encoding while encoding file
Merge pull request #53 from patacrep/include

Plugin include