BIRD-LG currently keeps log files indefinitely. This patch allows
setting the number of days logs should be kept for by adding
a `LOG_NUM_DAYS` parameter in the configuration files.
This change is backwards compatible: Running the updated code with
old configuration files will keep logs indefinitely as before; new
deployments based on the example configuration will keep logs
indefinitely.
Add the options
```BIND_IP = "0.0.0.0"
BIND_PORT = 5000```
which allows to bind lgproxy.py to an IP/interface.
As ports on routers shouldn't be exposed too much, it probably also makes sense to others to have this function. Tested.