dbNSFP 4.4a update

[erikyao]

This PR update dbNSFP plugin to version 4.4a. Major changes include:

1. Parser for 4.3a is refactored into V1; a new V2 parser introduced new document structure.
2. Mappings are updated accordingly.
3. For both V1 and V2 parser, a new column-wise configuration data structure is enabled by Column class.
4. For V2 parser, a new field protein wraps up 27 former fields aa, genename, geneid, transcriptid, proteinid, uniprot, hgvsc, hgvsp, appris, gencode_basic, tsl, vep_canonical, refcodon, codonpos, codon_degeneracy, sift, sift4g, polyphen2, mutationassessor, fathmm, provean, vest4, revel, mvp, gmvp, mpc, and aloft
5. For V2 parser, the former 27 field values wrapped to protein field are transformed from a dict of list values to a list of dicts