Better error reporting for scisample

Nobody has claimed this yet.

Summary
Make scisample error reporting more like study validation error reporting.
What is the current behavior?

```
2020-10-16 13:30:36 - ERROR - Sampler data is invalid
Traceback (most recent call last):
{ FIFTY-TWO lines of traceback }
codepy.scisample.utils.SamplingError: Sampler data is invalid
```

What is the desired behavior?

Reporting like that for study validation error reporting.
```
2020-10-16 13:30:53 - ERROR - Error in phase or flavor data for run-generate-baseline
2020-10-16 13:30:53 - ERROR - '01:00' does not match '^([0-9][0-9]-)?[0-9]{1,2}:[0-9][0-9]:[0-9][0-9]$'

Failed validating 'pattern' in schema['properties']['walltime']:
{'pattern': '^([0-9][0-9]-)?[0-9]{1,2}:[0-9][0-9]:[0-9][0-9]$',
'type': 'string'}

On instance['walltime']:
'01:00'
2020-10-16 13:30:53 - ERROR - Study is missing data, cannot write a maestro specifiation
```

Start by locating the current scisample SamplingError reporting and compare it with the study validation error-reporting path. Reproduce the invalid sampler-data case and make the output include the validation details and final error message in the style shown; confirm the traceback is replaced by the requested validation report.

Written by the indexing model from the issue text.