Added new config options to conf file reference
modified:   pbm-conf-reference.yml
# compression:
# compressionLevel:
+# Save oplog slicing without the base backup
+# oplogOnly: false
+
#==========================Backup Configuration============================
# Adjust priority of mongod nodes for making backups. The highest priority
#backup:
# priority:
+# Set a compression method and level
+# compression:
+# compressionLevel:
+
#==========================Restore Configuration===========================
# Options to adjust the memory consumption in environments with tight memory bounds.
