Added devices CryLas Laser and CryLas Attenuator

2 devices: CryLasLaser and CryLasAttenuator, both using serial communication

Both devices are very likely to be used together, hence it might make sense to keep them in the same file.

I needed to add methods to read/write bytes in comm/serial for the communication with CryLasAttenuator.

A small lookup table is needed in method set_repetition_rate of the CryLasLaser, is there a better way to implement it?