Miniwdl-lsf

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+ Add support for runtime hint `lsf.time` to specify the time limit
for the job in minutes. Passed to bsub with the `-W` option.

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+ Update memory reservation to use "-R rusage[mem=...]" instead of "-M".
To use "-M", set "memory_limit_multiplier" in configuration to a
positive value.
+ Support config option "memory_limit_multiplier" to set a hard limit
on memory usage.

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+ Update log location on retry
+ Correct memory calculation

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Initial release with the following features:

+ Utilize miniwdl's singularity backend to create a singularity command that
is then submitted using bsub.
+ Create a singularity image cache so singularity images are available on
the cluster nodes.
+ Support for ``cpu`` and ``memory`` runtime attributes.