initial code for .cha importation

[lucasgautheron]

• [x] tests
• [x] documentation
• [x] implementation

[lucasgautheron]

@alecristia, in order to write the tests and define the desired behavior of the conversion routine, can you help me write the truth values of the output CSV for the 20 first lines here ? https://gin.g-node.org/LAAC-LSCP/vandam-data/src/master/annotations/cha/raw/BN32_010007.cha

I have made it easier for you : https://docs.google.com/spreadsheets/d/11XRJM_Ab9B1GwWTERZCYQsrEVB9Ly8ulPktEAuTLK0U/edit#gid=542431292

Thanks :)