re-design the 'required' option

[julien6387]

push the definition at application level idea is to declare at once :

• the programs that are always required
• the programs that can be optional if another one is running

something like: <all_of>program_x, program_y, program_z</all_of> <one_of>program_a, program_b</one_of> <one_of>program_00, program_01, program_02</one_of>