Fix picard heapspace error in align rule

In the Singularity image for picard, the default heapsize is too small,
leading to crashes in the pipeline when the rule 'align' runs out of
heap space. The solution is to explicitly specify the heap space that
picard can use, thereby overriding the default value that is set in the
Singularity image.

This issue was reported on capture-lumc-wrapper, see
https://git.lumc.nl/klinische-genetica/capture-lumc/capture-lumc-wrapper/issues/26
for details.
6 jobs for hotfix-2019-07-17 in 43 seconds (queued for 1 second)
Status Job ID Name Coverage
  Sanity
failed #4166
docker
test_sanities

00:00:43

failed #4161
docker
test_sanities

00:01:41

failed #4137
docker
test_sanities

00:00:42

 
  Dry Run
skipped #4138
docker
test_dry_run
 
  Integration
skipped #4140
slurm
test_integration
skipped #4139
docker
test_integration_singularity
 
Name Stage Failure
failed
test_sanities Sanity
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