Change database dump format + add import & export scripts

The new format allows for downloading and importing only a part of the
database - useful when only the metadata is required - and doesn't
include the wasteful preformatted HTML cache.

This also ensures that the new import.sql script is actually usable and
in sync with the actual database. The old schema.sql was neither.

(And this simplifies my backup scripts)

.gitignore

@@ -6,3 +6,4 @@
 indexer/target
 web/target
 util/.config
+dl/