Support generating a database from a single file or code snippet

[aeisenberg]

Often users want to test out their queries on a small, custom-made database. The extension should facilitate the creation of small, simple databases from a single file or a selection.

In a single command, the user should be able to convert the current buffer (or the current selection in the current buffer) into a database, and then automatically import that database.

It might be the case that the user needs to explicitly specify a language. We also need to consider autobuilds. Not sure how that is going to come into play.