config: introduce attr config structure

Signed-off-by: Federico Vaga <federico.vaga@cern.ch>
Acked-by: Alessandro Rubini <rubini@gnudd.com>
config: seq_num start from 1

In output configuration, 0 will mean "do not change seq_num". Any other
value will be assigned to current_ctrl->seq_num

Signed-off-by: Federico Vaga <federico.vaga@cern.ch>
Acked-by: Alessandro Rubini <rubini@gnudd.com>
config: implement configuration system

Signed-off-by: Federico Vaga <federico.vaga@cern.ch>
Acked-by: Alessandro Rubini <rubini@gnudd.com>
config: allow to write current-control

Signed-off-by: Federico Vaga <federico.vaga@cern.ch>
Acked-by: Alessandro Rubini <rubini@gnudd.com>
tools/zio-control: a new GUI interface to read/write current_control

This interface allow you to inspect the current control of a channel.
You can change its attribute and the trigger's attributes.

At the moment, it is not possible to change the trigger type from this
interface.

Signed-off-by: Federico Vaga <federico.vaga@gmail.com>
Acked-by: Alessandro Rubini <rubini@gnudd.com>
UNTESTED zio-trigger.h: on output configure device before trigger fire

Signed-off-by: Federico Vaga <federico.vaga@gmail.com>
Acked-by: Alessandro Rubini <rubini@gnudd.com>
TMP do not use cset name