added a MAIN_DIR variable, and tweaked the conf sample and cron files to reflect how this is deployed in practice

sqlite_backup.conf-sample

@@ -1,20 +1,16 @@
 #
 # SQL dump backup directory
 #
+MAIN_DIR=/path/to/base/directory
 # backup file details
-BU_DIR=/path/to/directory/for/backups
+BU_DIR=$MAIN_DIR/backups
 # each backup will start with this basename
 BU_FROOT=preferred-basename
 #
 # location of sqlite database
-DB_DIR=/path/to/database/directory
+DB_DIR=$MAIN_DIR/data
 DB_FILE=your-db.sqlite3
 #
-# docker compose settings
-DC_DIR=/path/to/directory/containing/your/docker-compose.yml 
-# this is the name at the top of your docker-compose.yml stanza describing the container running SQLite
-DC_CONT=name_of_your_container
-#
 # Reporting
 #
 # email address to send reports to, and subject