Gripper check now uses firmware build date.

Gripper version 1.1.242 is the legacy gripper version,
and other 1.x.x grippers are invalid firmware versions. To avoid the
clashing of Manufacturing 1.x.x grippers and RSDK 1.1.x gripper
versions, I switched the check use gripper firmware dates. That way, any
recently built manufacturing or RSDK gripper will pass without warning
or error. Older build versions will warn, and any date as far back as a
bad firmware version will fail.

Also, removed deprecated Gripper.hardware_version() function.
Potentially use the (date - 1) of the coupled Mfg release (3.1) for the max 'warn' time.

- Original concept was that the current SDK release and the coupled Mfg release would be 'okay' (no messages), as those are the versions of a freshly updated robot/gripper, and the versions of a newly, out-of-the-box RSDK robot, respectively. Similarly, any special cased versions in 'okay' - like the Legacy version - would be okay, no message.
- Likewise, anything newer or older that didn't explicitly fall in the 'warn' or 'fail' specs, would also 'warn' in case people bought new grippers that somehow were silently not backwards compatible.

I can see why you took out the wildcards, and arrays of checking - it would make it more complex to do it in this date-based approach.  It probably works fine to do just these thresholds.

Could potentially put the 'okay' field in later as a patch as a "max 'okay'" threshold, but it would be a bit trickier to place, and again, probably fine until needed...