[settings] improve settings in pprzcenter

- check box for faster enable/disable
- loading from modules
[settings] add a few more settings in modules
[settings] variable size modules settings area
[settings] add settings directly inside modules files
[settings] allow several groups of settings in modules
[settings] move settings to module files and remove old files
[settings] fix example conf
fix conf_example
remove another unneeded settings file
[settings] select new modules' settings by default
[ocaml] remove leading white space when get tree values
[conf] update all example airframe for new modules' settings
[settings] remove settings from automatically unloaded modules
[modules] fix modules' settings
[ocaml] md5 sum target dependent due to unloaded settings
[paparazzicenter] settings area adapt its size (no more scrollbar)
Merge pull request #834 from paparazzi/modules_settings

let's see what's happening then