Beckhoff: archive old plc code and runner repos

[rerpha]

When #6153 is finished, and a cycle has completed, we should archive the repositories previously used for controlling beckhoffs. These are:

• https://github.com/ISISComputingGroup/EPICS-MCAG_Base_Project - Was running on IMAT for the rotation/z of their stage

• https://github.com/ISISComputingGroup/BeckhoffPLCCode - Running the CRISP jaws
  We should remove these as submodules as well - they are currently built & shipped on release.

• https://github.com/ISISComputingGroup/EPICS-ioc/tree/master/BKHOFF should also be removed, we are using the TC ioc instead.

• https://github.com/ISISComputingGroup/EPICS-motor/blob/master/motorApp/Db/motorUtil.db has a reference to BKHOFF_01 in the moving calc - this should be removed: https://github.com/ISISComputingGroup/EPICS-motor/blob/4f39c98ba1c1672c8dce478a26ddb3b180af0a9e/motorApp/Db/motorUtil.db#L80

Acceptance criteria

• Above repos + IOC are archived
• the respective submodules for the archived repos are removed

[rerpha]

can now be done. "will not be moved until they have been updated" - SC

[rerpha]

• Archived https://github.com/ISISComputingGroup/BeckhoffPLCCode
• remove old crisp course jaws code EPICS-TwincatMotor#2
• add comment for removal of crisp jaws code EPICS-ioc#839
• Ticket6854 #8272

There isn't really anything to test here as we never tested the old code anyway (actually we currently don't do much for the new code either but #7552 will sort this)

I have left in the PLC_VERSION macro as it will be used in the future if there are breaking changes in the PLC code.