Add support for BOINC Universal Docker Application (BUDA).

[davidpanderson]

This lets you run arbitrary Docker applications using a single
BOINC app (and one app version per platform).
The Dockerfile and science executables are in the workunit.

The script tools/submit_buda lets you test this.
Basic tests were successful.

2) Unify the scripts for testing job submission The 'test' assimilators (sample_assimilate.py and sample_assimilator.cpp) do the same thing: they copy result files to

/results// (if 1 output file) /results//_i (if >1 output file) where is 0 if WU is not in a batch ... and they write error code to _error if the WU errored out Scripts to submit jobs: submit_job submit_batch submit_buda Script to query jobs: query_job This works for either jobs or batches, as long as the app uses one of the above assimilators 3) Add plan class 'docker' to plan_class_spec.xml.sample Fixes #5896

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 22 lines in your changes missing coverage. Please review.

Project coverage is 10.73%. Comparing base (abfea4c) to head (2d35fd5). Report is 5 commits behind head on master.

Files with missing lines	Patch %	Lines
sched/sample_assimilator.cpp	0.00%	16 Missing :warning:
sched/script_assimilator.cpp	0.00%	6 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #5897 +/- ## ============================================ - Coverage 10.73% 10.73% -0.01% Complexity 1068 1068 ============================================ Files 280 280 Lines 36598 36604 +6 Branches 8482 8484 +2 ============================================ Hits 3930 3930 - Misses 32279 32285 +6 Partials 389 389 ``` | [Files with missing lines](https://app.codecov.io/gh/BOINC/boinc/pull/5897?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=BOINC) | Coverage Δ | | |---|---|---| | [sched/script\_assimilator.cpp](https://app.codecov.io/gh/BOINC/boinc/pull/5897?src=pr&el=tree&filepath=sched%2Fscript_assimilator.cpp&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=BOINC#diff-c2NoZWQvc2NyaXB0X2Fzc2ltaWxhdG9yLmNwcA==) | `0.00% <0.00%> (ø)` | | | [sched/sample\_assimilator.cpp](https://app.codecov.io/gh/BOINC/boinc/pull/5897?src=pr&el=tree&filepath=sched%2Fsample_assimilator.cpp&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=BOINC#diff-c2NoZWQvc2FtcGxlX2Fzc2ltaWxhdG9yLmNwcA==) | `0.00% <0.00%> (ø)` | |