D Switch all data storage in bw2data to SQLite

[cmutel]

We now have an evil mix of pickle files, JSON files, and SQLite databases. It is very, very dumb. The original justification was that loading 500.000 locations codes (during regionalized LCA) was much faster in one file than a big database query, and JSON allowed configurations to be edited without having to know how to use a relational database. These reasons are inadequate.

Specific tasks:

• D1 Migrate all data storage in bw2data to SQLite databases

Nice-to-have:

• D2 Use the SQLite text search instead of a separate Whoosh search index

[cmutel]

mapping was fixed some time ago with the switch to bw_processing.

databases removed in #112.