manage main config using an INI file.

initial step to handle the main configuration of coffer using an ini
file. For now add econfig tdependancy and handle the HTTP configuration.

Example of config file:

    [http main]
    listen = 7000

will listen all interfaces on the port 7000. Multiples HTTP interfaces
can be set.

listen is under the form [IP:]Port, where IP is an IP v4 or v6.

To setup an SSL connection add the following section:

    [http somessl]
    listen = 7001
    ssl = true
    cert_file = cert.pem
    cert_key = cert.key

Other ssl options are password, cacert_file. Check the elrang
documentation for more informations about these options. Multiple ssl
interfaces can be set.

Partially answer to #11 .