Suggest 'related' workflows

For instance using this naive SPARQL that finds workflows using the same docker images:

```sparql
PREFIX cwl:
PREFIX docker:
PREFIX rdf:

SELECT DISTINCT ?g2 (COUNT(?image2NoVersion) AS ?c)
WHERE {
BIND( AS ?g1)
GRAPH ?g1 {
[] docker:dockerPull ?image1 .
BIND (REPLACE (?image1, ":.*", "") AS ?image1NoVersion)
}

GRAPH ?g2 {
[] docker:dockerPull ?image2 .
BIND (REPLACE (?image2, ":.*", "") AS ?image2NoVersion)
}
FILTER (?g1 != ?g2)
FILTER (?image1NoVersion = ?image2NoVersion)
}

GROUP BY ?g2
ORDER BY DESC(?c)
```

Gives with ranking:

| g2 | ?c |
| --- | --- |
| http://sparql:3030/cwlviewer/github.com/genome/arvados_trial/blob/202b43b7449485a317c857d62ca7d39196764e65/detect_variants/detect_variants.cwl| 42 |
|http://sparql:3030/cwlviewer/github.com/genome/arvados_trial/blob/202b43b7449485a317c857d62ca7d39196764e65/pipeline.cwl| 42 |
|http://sparql:3030/cwlviewer/github.com/genome/cancer-genomics-workflow/blob/202b43b7449485a317c857d62ca7d39196764e65/detect_variants/detect_variants.cwl| 42|
| http://sparql:3030/cwlviewer/github.com/genome/cancer-genomics-workflow/blob/202b43b7449485a317c857d62ca7d39196764e65/pipeline.cwl| 42|
| http://sparql:3030/cwlviewer/github.com/genome/arvados_trial/blob/202b43b7449485a317c857d62ca7d39196764e65/varscan/workflow.cwl| 22|
| http://sparql:3030/cwlviewer/github.com/genome/cancer-genomics-workflow/blob/202b43b7449485a317c857d62ca7d39196764e65/varscan/workflow.cwl| 22|
| http://sparql:3030/cwlviewer/github.com/genome/arvados_trial/blob/202b43b7449485a317c857d62ca7d39196764e65/strelka/workflow.cwl| 8|
| http://sparql:3030/cwlviewer/github.com/genome/cancer-genomics-workflow/blob/202b43b7449485a317c857d62ca7d39196764e65/strelka/workflow.cwl| 8|
| http://sparql:3030/cwlviewer/github.com/genome/arvados_trial/blob/202b43b7449485a317c857d62ca7d39196764e65/pindel/workflow.cwl| 6|
| http://sparql:3030/cwlviewer/github.com/genome/cancer-genomics-workflow/blob/202b43b7449485a317c857d62ca7d39196764e65/pindel/workflow.cwl| 6|
| http://sparql:3030/cwlviewer/github.com/genome/arvados_trial/blob/202b43b7449485a317c857d62ca7d39196764e65/strelka/process_vcf.cwl| 4|
| http://sparql:3030/cwlviewer/github.com/genome/arvados_trial/blob/202b43b7449485a317c857d62ca7d39196764e65/varscan/bgzip_and_index.cwl| 4|
| http://sparql:3030/cwlviewer/github.com/genome/cancer-genomics-workflow/blob/202b43b7449485a317c857d62ca7d39196764e65/strelka/process_vcf.cwl| 4|
| http://sparql:3030/cwlviewer/github.com/genome/arvados_trial/blob/202b43b7449485a317c857d62ca7d39196764e65/mutect/workflow.cwl| 2|
| http://sparql:3030/cwlviewer/github.com/genome/cancer-genomics-workflow/blob/202b43b7449485a317c857d62ca7d39196764e65/mutect/workflow.cwl| 2|