Build system cosmetics

I slightly changed the electron:dev command :

• remove gpu acceleration : not working on (some?) linux
• remove bsb:start from the command so the trash goes in electron:dev and the interesting part (type errors) are in bsb:start. You can start electron:dev from any terminal that you can ignore and bsb:start from you dev environment to have a clean log.

I also hid some reason warnings that I feel are useless (correct me if you don't):

• module opening shadows an identifier. It can be a source of mistake, but it is usually a feature. (44, 45)
• implicit elimination of optional arguments (48)
• Missing fields in a record pattern (9)