Add MySQL adapter support

- config/database.js.mysql: mysql storage template file
- config/database.js.redis: add unix socket option
- app/routes/api.js: allow unix socket connection with redis
- config/server.js: add unix socket option to redis section
- Gruntfile.js: use --debug-brk option
- README.md: update doc

Signed-off-by: Boris HUISGEN <bhuisgen@hbis.fr>