Fccd darks

Dear Karim,

I have only added one small line to the FastCCD dark notebook to reset cmCorrection after the first time it is used and before it is used again. Could you please merge this to master project? I am not 100% sure if it is totally required to reset cmCorrection but I think it may be safer to do so.

Please do not hesitate to contact me if you have any questions/concerns. Thanks very much. Best, Kiana