Simplify database initialization processus

[llaville]

It will be more simple now than ever to initialize database with new command db:create

By default, if you don't define a specific connection with the DATABASE_URL environment variable, CompatInfo will still use the SQLite database backend.

Composer scripts, that previously trigger setup database, were removed.

For integration with other projects, only one command is required : vendor/bin/compatinfo-db db:create