Reflectometry: Zero motors via beamline parameters

[ThomasLohnert]

For alignment of a reflectometry beamline, users should be able to redefine the zero position on a motor via the top-level beamline parameters (e.g. writing the new zero position to a PARAM:<name>:SETZEROAT PV). Unlike zeroing it at the motor level directly, this allows taking engineering corrections into account.
Therefore if I am at the zero position when I redfine the position my readback will instantly read back 0.

Requires:

• Reflectometry: Engineering Corrections #3541

Acceptance Criteria

1. Setting an offset parameter changes the sp and sp:rbv by the value given
2. I can zero a beam offset parameter. Works for:
   1. For detector offset
   2. For sample height offset
   3. For slit height offset (this means zeroing both jaw blades to correct place)
3. I can set a slit gap parameter zero (both blades are set)
4. I can set an angle offset parameter to zero
5. Close IOC Test Framework: Launch without running tests #4499
6. Log line must be printed to show definition from and to

Implementation Detail

1. Allow the motor to set zero so it is available to all motors. This should be a sequence record. With a button which does it.

[John-Holt-Tessella]

Pull requests:

• Add records to set the motor position EPICS-galil#35
• Test the set of motor at motor level. Also add facility to stop tests EPICS-IOC_Test_Framework#232
• Ticket4131 zero motors EPICS-IOC_Test_Framework#254
• Ticket4131 zero motors via beamline parameters EPICS-inst_servers#240
• Add alignment tab ibex_gui#982