MEDIUM: spoe/rules: Add "send-spoe-group" action for tcp/http rules

MEDIUM: spoe/rules: Add "send-spoe-group" action for tcp/http rules

This action is used to trigger sending of a group of SPOE messages. To do so,
the SPOE engine used to send messages must be defined, as well as the SPOE group
to send. Of course, the SPOE engine must refer to an existing SPOE filter. If
not engine name is provided on the SPOE filter line, the SPOE agent name must be
used. For example:

   http-request send-spoe-group my-engine some-group

This action is available for "tcp-request content", "tcp-response content",
"http-request" and "http-response" rulesets. It cannot be used for tcp
connection/session rulesets because actions for these rulesets cannot yield.

For now, the action keyword is parsed and checked. But it does nothing. Its
processing will be added in another patch.