Apps: Troubleshooting guide

[scblack321]

Begin writing up a troubleshooting guide for readthedocs.
Include such things as tips for debugging an application without having to submit a job through Tapis every time.
For example, once an app is run via a Tapis job it is generally much faster to debug by going to the execution
host and directly running the tapisjob.sh script that was generated by the job.
There are many variations on how to best do this. For example, using a runtime type of SINGULARITY on a
a TACC cluster, it would be necessary to use an idev session to run the script from a compute node so the apptainer module
can be loaded.