Limit number of processes required to complete Xsteps

[keiranmraine]

Hi @drjsanger, I've added an additional command line option -l which should provide the ability for the Implementation code to run in a restricted number of jobs with little modification to how it's handled elsewhere. I've also added a test for this function to ensure it's getting it correct, feel free to expand it:

$ prove -v -I lib t/cavemanImplement.t
...
    ok 1 - No limit, single value
    ok 2 - No limit, single value=1
    ok 3 - Limit matches max jobs, single value
    ok 4 - Limit matches max jobs, single value=1
    ok 5 - Limit = max jobs/2, 2 values (index_in=1)
    ok 6 - Limit = max jobs/2, value[0]=1 (index_in=1)
    ok 7 - Limit = max jobs/2, value[1]=3 (index_in=1)
    ok 8 - Limit = max jobs/2, 2 values (index_in=2)
    ok 9 - Limit = max jobs/2, value[0]=2 (index_in=2)
    ok 10 - Limit = max jobs/2, value[1]=4 (index_in=2)
    1..10
ok 3 - Indicies limits
...

In the SeqWare workflow you just need to ensure that the -l option is declared (at present only m/estep will interpret it).