Import data of EKP and NKP data of Potential project

[elpiankova]

Add import of Potential data from EKP and NKP devices.
These data are located in *.csv files (time, amount of points in*.set ) of some of sessions folders in: ftp://ftp.promis.ikd.kiev.ua/Potential/DECODED/<some_date>/pdata<some_date>/pd/ekp/00/ - for Plasma parameters sensor (EKP)
ftp://ftp.promis.ikd.kiev.ua/Potential/DECODED/<some_date>/pdata<some_date>/pd/nkp/0/ - for Neutral gas parameters sensor (NKP)