ability to add script plugins to oref0-pump-loop

[efidoman]

This PR adds the ability to inject custom script(s) to run synchronously at the end of every oref0-pump-loop. Any script files with executable flag set will be run as follows:

If the script file is placed in the plugins/every folder then the script runs at the end of every loop.
If the script file is placed in the plugins/once folder then the script once at the end of the current loop.

Script files placed in the plugins/once folder will be removed once run. This allows for a use case such as the following:

Logger and Lookout both call a pump utility called fakemeter that helps out users in offline mode by sending the current CGM (Dexcom) glucose value as a meter glucose value. This shows the glucose on the pump every 5 minutes and allows you to quickly see the current glucose value on the pump. Since this script requires communication with the pump, it will collide with oref0 pump communications on occasion. This oref0-pump-loop plugin capability will allow Logger and Lookout to run fakemeter synchronously at the end of the pump loop and avoid any radio collisions.

[scottleibrand]

Code looks good. If someone can post test results, I think we can merge this.

[efidoman]

needs a quick review again. I found an issue while testing where the plugins didn't run upon any loop failure. The intention is for plugins to run at the end of every pump loop regardless of pass or fail. Also, I updated the comments and logging a bit.

[efidoman]

Here's my latest test results that include the Logger PR to leverage this new plugin capability for running fakemeter:

Completed oref0-pump-loop at Wed Feb 27 08:28:30 EST 2019

Running plugin script (plugins/once/run_fakemeter.sh)... 
2019/02/27 08:28:31 connected to CC111x radio on /dev/spidev5.1
2019/02/27 08:28:31 setting frequency to 916.650
2019/02/27 08:28:31 model 522 pump
2019/02/27 08:28:34 disconnecting CC111x radio on /dev/spidev5.1
Completed plugin script (plugins/once/run_fakemeter.sh). 
Running plugin script (plugins/every/plugins.sh)... 
Plugins Starting - Wed Feb 27 08:28:34 EST 2019
Completed plugin script (plugins/every/plugins.sh). 
Running plugin script (plugins/every/yo.sh)... 
/root/myopenaps
Completed plugin script (plugins/every/yo.sh). 

Starting oref0-pump-loop at Wed Feb 27 08:29:03 EST 2019 with 1 second wait_for_silence:

[scottleibrand]

Moving it here won't help make it run on failures, as the fail function calls exit 1. You'll instead need to add run_plugins after update_display there as well as above.

[efidoman]

Thank you. I was not aware. I have updated run_plugins to run in both places so it runs either way.

[scottleibrand]

I just tweaked the placement to be more consistent between the two cases. LMK if you don't think that will do the right thing.

[efidoman]

LGTM

[scottleibrand]

Anything else before we merge?

[efidoman]

It's ready. I've been watching the logs and testing - works great.