WIP: Add initial restic support.

I've added a handler and example config file for restic. Since I'll be deploying this via Ansible, I'm not intending to write a helper, etc. But, I figured I'd share what basic progress I have made.

examples/example.restic

+[general]
+
+# The location of the repository in which to store backup snapshots.
+repo = /var/backups/restic
+
+# The repository password.
+password = some_password
+
+# AWS credentials to authenticate to S3-backed repositories.
+#aws_key =
+#aws_secret =
+
+# Create a snapshot to backup specified data.
+backup = yes
+
+# Remove snapshots according to a policy.
+# Defaults to 'no'.
+retention = yes
+
+# Check repository integrity and consistency
+# Defaults to 'no'.
+check = yes
+
+
+[backup]
+
+# Files and directories to backup when taking snapshots.
+# This option may be specified multiple times.
+#include =
+
+# Patterns by which to exclude files and directories from snapshots.
+# This option may be specified multiple times.
+#exclude =
+
+# A short string to help identify a snapshot.
+# This option may be specified multiple times.
+#tag =
+
+# Only backup files from the file systems on which the initially specified
+# files or directories reside.
+one_file_system = yes
+
+
+[retention]
+
+# Never delete the n last (most recent) snapshots
+keep_last =
+
+# For the last n hours/days/weeks/months/years in which a snapshot was made,
+# keep only the last snapshot for each hour/day/week/month/year.
+# When "retention = yes", above, default is to keep the last 7 backups, and
+# 2 each for daily, weekly, monthly and yearly backups.
+keep_hourly =
+keep_daily =
+keep_weekly =
+keep_monthly =
+keep_yearly =
+
+# Keep all snapshots which have all tags specified by this option (can be specified multiple times).
+#keep_tag =