New L0 0.2.1 => more protections

We made small modification on L0 and switch to hardware revision 0.2.1.
Nothing change about functionalities or usage, we just add some protections on specific signal that could spread a damage to an entire network and optimize some production things.

Those new protection circuits introduce unplanned propagation delay during detection. This delay result on an infinite loop during detection. We have to modify the modules firmware to take into account this new propagation time.

We will create a new 0.4.0 firmware revision that will be compatible with this New L0 revision. New shipped modules from now will be incompatible with firmware revision under 0.4.0.
This new L0 is compatible with older modules.
This new firmware is compatible with older modules.