Add support for Cosylab's new ads driver

[klauer]

Issue

A new ADS driver exists with a slightly different addressing format for records:

https://github.com/Cosylab/adsDriver

Its performance has been investigated well (and is reportedly good). pytmc should be able to support this module alongside m-epics-twincat-ads.

Implementation

A modification of the INP/OUT strings may be all that is required, but more investigation will be needed. Cosylab engineers indicated that a slight modification already exists and has been used.

Toggling between ADS libraries

Some environment variable or command-line option should be used in order to switch between formats.
Perhaps the environment variable could be used to set a default. A command-line option could be a per-execution override.