Add auto check functionality

CHECK_INTERVAL or SUB_CHECK_INTERVAL in module settings.
If set to 1, will check everytime.
Ever other number is for n days after last check.

FORCE_CHECK for check if repository has been setup os now renamed
FORCE_VERIFY but FORCE_CHECK is currently still honored but deprecated

all *function* shell scripts will abort if run on their own

Print info on last check time if set in info block

Internal updates:
All separator lines are now printf strings for central control.
All module used config/settings file names use $MODULE name
Check functionality is in its own file

borg.backup.settings-default

@@ -27,8 +27,13 @@ COMPRESSION_LEVEL="";
 # Blank passwords allowed for only key (if used, use keyfile)
 # See: http://borgbackup.readthedocs.io/en/stable/faq.html#how-can-i-specify-the-encryption-passphrase-programmatically
 ENCRYPTION="";
-# force repository check, default is off, set to true for check
-FORCE_CHECK="";
+# force repository verirfy, default is off, set to true for verify on every run
+FORCE_VERIFY="";
+# check interval, if 0 or negative number, no check will ever run
+# if empty fall back to default set
+# if set to 1 then every time the script runs
+# any other value it means ever n days, eg 90 would be every 90 days
+CHECK_INTERVAL="";
 # default is %Y-%m-%d
 # todays date, if more than one per day add -%H%M for hour/minute
 # it can also be "{hostname}-{user}-{now:%Y-%m-%dT%H:%M:%S.%f}"