DAE IOC: Change RUNSTATE_STR PV to actually be a string

[FreddieAkeroyd]

The DAE has both DAE:RUNSTATE (MBBI record) and DAE:RUNSTATE_STR (an alias for this) PVs. It seems slightly curious that the _STR PV is not actually a string. I checked genie_python and it uses DAE:RUNSTATE, I checked the ibex gui and it uses RUNSTATE_STR so would need a small change to use RUNSTATE instead. My motivation for this is both consistency and also to allow adding a block to provide a string representation of the run state, SECI did this automatically for you but I'm not sure if it is really needed, Mantid for example use the _ICPevent.txt file. However in case it suddenly turned out to be needed, I though it would be worth having the compatability option.

[FreddieAkeroyd]

To test:

• [x] genie_python: no need, does not use RUNSTATE_STR (just uses RUNSTATE)
• [x] ibex_client: check the runstate is displayed correctly on dashboard