At last, I've found the solution : there are two versions of Cura json files for the A10M. One of them doesn't works for me.
The good one is on Geeetech forum:
http://www.geeetech.com/forum/viewtopic.php?p=89761&sid=c51926817bf3f514d4c61542c44767f7
There are some changes to make in Cura Machine Settings : size of the printer setting is wrong, change the width, depth and height (X 235 Y 235 Z 260. And in Left and Right extruders tab: Size nozzle 0.4 and material 1.75 mm.
In Cura all the G-code is in the Printer tab. Extruders tabs are empty. And it works fine even for the prime tower. I think I'll need to configure its size for a better purge but it is already a big improvement.
In Start G-code, I've added G-code for drawing two straight lines before beginning printing and in End G-code to bring the bed at the front for easy removal of the print.
Here is my Start G-code
G28 ;Home
G29 ;For ABL
G1 Z15.0 F6000 ;Move the platform down 15mm
;Prime the extruder
G92 E0
G1 X7 Y25 Z.3 F5000
G1 X7 Y180 Z0.3 F1500 E0
G1 X11 Y180 Z0.3 F5000
G1 X11 Y25 Z0.3 F1500 E0
G92 E0
End G-code
M104 S0;Cooling the heat end
M140 S0;Cooling the heat bed
G92 E1
G1 E-1 F300
G28 X0 Y0;Home X axis and Y axis
G1 Y220 F6000
M84
Left Extruder and Right Extruder tabs are empty
Hope it will help some users. If someone want the explanation in French, let me know.