several changes to namespaces.py
add sort to .belns file values
closes #23
moved ns/eq value exclusion to datasets.py
refs #27
fixed/added exclusion of G01, G02, G15, G17 subbranches frm MESH bp
closes #38
changed namespaces.py to retain all SDIS and SCHEM ns values
refs #26
moved hgnc/mgi/rgd map from namespaces.py to datasets.py