Add delay between Polls for devices in Modbus RTU

[pturmel]

Beta announcement for my new Modbus module. It implements this inter-request delay in its Client driver type:

Automation Professionals' Advanced Modbus Driver

Automation Professionals is pleased to announce the first beta for its Advanced Modbus Driver, for Ignition version 7.9. Key features: Server mode, emulating one or more slave devices, using any of the three typical connection types, including simultaneous connections of multiple types. Client mode, incorporating all three connection modes in one driver. Support for Modbus Function Codes 20 and 21, File Records. Configure protocol tweaks for troublesome devices per slave unit, enabling suppor…