Make all the bnet files from PyBoolNet/Repository openable in R BoolNet.

[nanls]

Hi!

Of the 25 bnet files I found in PyBoolNet/Repository, 18 are openable in R BoolNet, but for the 7 others (mostly toy BNs), the header targets, factors is missing.

This PR is just about adding these headers. :)

List of the file changed:

• PyBoolNet/Repository/n7s3/n7s3.bnet
• PyBoolNet/Repository/n6s1c2/n6s1c2.bnet
• PyBoolNet/Repository/n12c5/n12c5.bnet
• PyBoolNet/Repository/n3s1c1a/n3s1c1a.bnet
• PyBoolNet/Repository/remy_tumorigenesis/remy_tumorigenesis.bnet
• PyBoolNet/Repository/n3s1c1b/n3s1c1b.bnet
• PyBoolNet/Repository/n5s3/n5s3.bnet

Also, I find the docstring of FileExancge.primes2bnet() misleading. What about changing it to

Saves Primes as a bnet file, -> optionnaly <- including the header "targets, factors" for compatibility with :ref:installation_boolnet.

(Note that the default is without header)

[hklarner]

• I left out the targets, factors header intentionally: being compatible with BoolNet is optional, not required
• if you want to export for BoolNet you would load the primes from the repository and then export with header=True
• I agree about the doc string: feel free to change that