set default GPU to K80->P4 in BEAST task; parameterize beagle_order

[tomkinsc]

set default GPU to K80->P4 in BEAST task; expose beagle_order as a task input

[dpark01]

One request -- can we parameterize with some boolean beagle_double=true that turns into either -beagle_double or -beagle_single on the command line? In >90% of the xmls I've run, we need double precision to converge well, but every once in a while, single-precision is enough and the speed gains are huge. The best performance/$ is actually on a T4 but only if you're running single-precision.

[dpark01]

Is this ready to merge?

[dpark01]

Ooh actually this might be a good opportunity to try out / implement some of the thinking in #130. We could:

1. Add -save_every 100000 -save_state checkpoint.state to the beast invocation in the command block
2. Add checkpointFile: "checkpoint.state" to the runtime block of the task
3. Add some bash conditionals that check for the existence of the checkpoint.state file and add -load_state checkpoint.state to the beast invocation if the file exists.
4. Maybe also accept the checkpoint file as an optional input File??

Cromwell seems to only support one such special file, so we can't do the beast_log too while we're at it. Not sure if the checkpoint file actually contains all the log data as well or if it's only tracking a single state...

[dpark01]

Actually I'll just merge this as-is now and we can work on #130 later. Looking to tag a new release here before the holidays.