Added ledger backup/archival script.

Added basic ledger backup/archival script.

backup.sh

@@ -0,0 +1,16 @@
+#!/usr/bin/zsh
+
+# determine start and end years
+startyear=$1
+endyear=$2
+
+cd ${LEDGER_DIRECTORY}
+
+cp ${LEDGER_FILE_NAME} ${LEDGER_FILE_NAME}.bak
+ledger -b ${startyear} -e ${endyear} print > ${LEDGER_FILE_NAME}-${startyear}.dat
+ledger equity assets > equity.tmp
+ledger -b ${endyear} print > ledger.tmp
+
+cat template.dat equity.tmp ledger.tmp > ${LEDGER_FILE_NAME}
+
+rm -r equity.tmp ledger.tmp