input.Makefile: Staging tables installation: Store install logs for full-DB exports in new logs subdir of main dir. This also fixes a bug where the install log itself was considered a DB export, because its extension was .log.sql.
input.Makefile: Staging tables installation: Store install logs for full-DB exports in new logs subdir of main dir. This also fixes a bug where the install log itself was considered a DB export, because its extension was .log.sql.