genie_python: Add function to get runtime

[DominicOram]

As an instrument scientist on Larmor (RD) I would like to be able to get the current runtime of the run through genie_python. This function should return an integer of how many seconds I have been running.

Acceptance Criteria

• There is a get_runtime function in genie python that does the above
• There are system_tests for this function

[FreddieAkeroyd]

Should we look to returning a float for better accuracy? We'd need to adjust the underlying PV and a few other bits

[FreddieAkeroyd]

There is already a get_run_duration function the the genie python dae api , it also has optional period support

[FreddieAkeroyd]

It seems RD requires something slightly different, he would like a duration since run start that does not take into account pause/waiting etc. get_run_duration above does allow for this, and is what is displayed on the dashboard as "run time". What RD requires is (time now - time run started) - we may need to give this a different name to "runtime" to avoid confusion.

[daryakoskeroglu]

https://github.com/ISISComputingGroup/system_tests/pull/82

[daryakoskeroglu]

https://github.com/ISISComputingGroup/genie_python/pull/348

[daryakoskeroglu]

https://github.com/ISISComputingGroup/IBEX/commit/94dac47c4fdd06b426795045c649b40d6c1ce708

[DominicOram]

Works great, minor comments on the PRs, sorry. Also, can you drop an email to the instrument scientist to let them know it will be there next cycle?