Add restriction to prevent over-threading.
Modify the cache names for nxf_singularity to separate it from
singularity cache.
Add restriction to prevent user's mis-usage of clusterOption in params.

The executor contents are moved inside of profile, so that it could
run individually without cross-talking.

so that is is more clear to be able to reuse in profile

move clusterOptions and scratch out of executor, and move them into
process.

delete spaces

When solving the conflicts from the recent update on config file from nf-core side, the cachedir is reset to older version. 
Have to modify it to match our cluster setting.

Deleted the out of date one

Remove the out of dated resourcelimits from params to process.
Changed the igenome_base from /fdb/igenomes to /fdb/igenomes_nf.

the recent update of cluster hardware.