Make models better for efficient queries

[TG1999]

Currently we store packagerelatedvulnerabilities in one table, either a package fixes a vulnerability or affected by some vulnerability, the combination of package and vulnerability is stored in the same table with a flag for fix, We should segregate this data in 2 tables.

See also:

• The query for affected and fixed packages should be abstracted as methods on the models (and/or on a model manager) #595
• For packages, enable sorting versions in database queries, or store additional computed fields #1549

[pombredanne]

Here are the diagrams we discussed in today's community call: