Define 'load' for command

[yanlinlin82]

Set 'load' for each command (default is 1), to limit parallel instance according to total CPU core.

#[require="${REF}" input="${FQ1}" input="${FQ2}" output="${BAM}" load="${THREAD}"]
bwa mem ${REF} ${FQ1} ${FQ2} -t ${THREAD} | samtools view -Sb - > ${BAM}