Make pythonIoc pip installable

[thomascobb]

At the moment it is an EPICS module that embeds Python. This PR will make it a Python module that embeds an EPICS IOC.

[thomascobb]

@Araneidae this is working apart from a couple of things with devIocStats

1. We don't use the epics build system to make ioc.db, and dbLoadDatabase doesn't like ioc.template because it contains the msi "substitute" command. I can get round this in Python
2. Loading devIocStats gives: Error (511,35) PV: TS-DI-TEST-01:SYSRESET Proc subroutine (SNAM). This is a mystery to me as the relevant routine appears when you do strings on the extension that I built. Any ideas?

[thomascobb]

I'll add the CI and more tests when these things are working...

[thomascobb]

@mdavidsaver notes that 2. is because registerAllRecordDeviceDrivers() isn't handling function(). He'll look at modifying this in EPICS base...

[thomascobb]

Ok, this should be ready to review again, just docs left to do

[thomascobb]

Once we have a 1.4.1 release of epicsdbbuilder, then I can regenerate Pipfile.lock with DLS deps, then I think I'm done here

[Araneidae]

Ignore!