Brake computing and timeout changes

The braking angle is not starting from 0 but from the current angle
given by the sensor. This avoid oscillating if there is angle overshoot
after sharp release of stick from big angle.
Timeout is computed differently and avoid errors that could be due to
the wind effect or the overshoot mentionned before. Moreover, in the
last timeout code , timeout could never be reached.
Add wind compensation and i_term init

Untested, give a try tomorrow.
changed wind_comp type from int32 to float
Add smooth angle decrease on stick release

Have to check to loiter init : with or without stopping point
Disable soft start & change smooth decrease/brake

Disable loiter feedforward soft start to try the different loiter init
cases (in order to fix the stop and go).
The derivative term will be started softly once the right loiter init
has been found and only if there is a twitch at loiter engage.
The brake mode engaged too early, it has to engage only once copter has
reached horizontal position (after the smooth decrease).
Log of hybrid variables

- Take off in Hybrid doesn't starts loiter
- Loiter timeout sometime seems not ok
Add derivative term to roll/pitch stab controllers

Have to run autotune and check if D_term usefull. if not, re-enable
stick filter
Brake/loiter commands mix (loiter soft start off)

Temporary commit. Did a flight quite promising, I'll make the changes I
think usefull and trye something else. Anyways, the command mix seems
better than loiter soft start.
Acc Wind_comp & Smooth Stick release

WARNING : THIS NEW SMOOTH STICK RELEASE CODE HAS NOT BEEN TESTED, TAKE
CARE WHILE RUNING IT.
CH7 must be off for best behaviour, set it on to check program
differences.
Wind comp works, it's been tested.
Fix compilation bug - cf details in previous post
Disable Stab D_term and fix stick release filter

It has to be tested, I've changed the condition to compute the filtered
roll/pitch + used floats to avoir cast errors.... Hope it's gonna work
Fix brake_timeout bug and Wind_comp if !landed

Also fix some transitions between modes and now we manage everything
from command and not sensor, this avoid unstabilities.
Merge pull request #4 from Ju1ien/temp-to-merge

Temp to merge branch merged to master.
This current code works well.
TO-DO :
- Tune smooth_filter (5-7) and brake rate (7-10)
- Try to increase deadband to see if better using loiter controller for very little stick inputs
- Test the code in windy conditions