Add missing packages

[iamashwin99]

Few packages that are already there in spack and require minimal effort include :

• nfft
• pnfft
• berkeleygw
• sparskit
• etsf-io

[fangohr]

For etsf-io, we can perhaps continue #13 ?

[iamashwin99]

I had a look at #13, i felt that it would be easier to add the 3 lines than to deal with the merge conflict that comes when rebasing with that MR.

[fangohr]

Just close #13 when you have extract the relevant information and used it elsewhere.