Fix player abilities api

[Bafbi]

Objective

#515

• Be able to overwrite the ablitities change of the gamemode.
• Only overwrite one flag doen't affect the rest of the flags to be affected by the gamemode change
• Work on Client init

Solution

• Change some systems name.
• Sync gamemode abilities only if not overwrited.
• Create a page in doc for the module.
• Add demo in cow_sphere.

ps : What I did is a shitty solution, I'm going to think of a better one, consider this as a draft.