Fix alias parsing and release fixed database

[reece]

Something changed last year in a way that caused the entire defline to be loaded as an alias. seqrepo releases since last June or so are affected. This affects NCBI and Ensembl.
See comments in cli.py::load()

This issue is a master list for work to comprehensively fix parsing. It will need to span several package and data releases.

0.5.5

• Move defline parsing to separate fx and add tests (Move defline parsing to separate fx and add tests #78)
• Create mechanism to modify/fix existing databases in place (Create mechanism to modify/fix existing databases in place #79)
• Require Ensembl aliases to have a version and remove unversioned from db (Require Ensembl aliases to be versioned and drop unversioned from database #80)
• Reject whitespace in aliases and fix existing db (Reject whitespace in aliases on loading and fix existing db  #83)
• Drop support for gi and genbank and remove from db (Drop support for gi and genbank and remove from db #81)
• Release a new snapshot with the above fixes