MEDIUM: spoe: Parse new "spoe-group" section in SPOE config file

MEDIUM: spoe: Parse new "spoe-group" section in SPOE config file

For now, this section is only parsed. It should have the following format:

    spoe-group <grp-name>
      messages <msg-name> ...

And then SPOE groups must be referenced in spoe-agent section:

    spoe-agnt <name>
        ...
	groups <grp-name> ...

The purpose of these groups is to trigger messages sending from TCP or HTTP
rules, directly from HAProxy configuration, and not on specific event. This part
will be added in another patch.

It is important to note that a message belongs at most to a group.