Novelec part updated

MEAS? cmd changed. Now READ? is called instead.

Keithley part : support for 6517.

6517 model management added and tested :
-> problem to check : no SRQ !

- SRQ management changed :
* ReadStatusByteRegister method added
* IsSrqLineUP added

- command abort added for SCPI Keithleys

- minor change for integration time

- Integration Mode available for DDC/SCPI devices
- tests done with a K617 (DDC) and a K6485 (SCPI)

- integration mode OK (tests done with K_486)

- TODO: DDC/SCPI
integration time for ScanServer compatibility.
report config for all DDC
add configuration in SCPI start command

- trigger mode and buffer size management added.
- TODO: DDC/SCPI
integration time for ScanServer compatibility.
SRQ management for Keithley Integration mode

support added for Keithley 6517