rename pre/post/backup-failure-hook to -command

This change is meant to be more compatible with holland 2.0
which has a more sophisticated notion of a hook and to more
clearly note that these "hooks" are just running shell commands

holland/commands/backup.py

@@ -122,7 +122,7 @@ def purge_backup(event, entry):
         LOG.info("auto-purge-failures not enabled. Failed backup not purged.")
 
 def call_hooks(event, entry):
-    hook = event + "-hook"
+    hook = event + "-command"
 
     if entry.config['holland:backup'][hook] is not None:
         cmd = entry.config['holland:backup'][hook]

holland/core/spool.py

@@ -222,9 +222,9 @@ def __cmp__(self, other):
 backups-to-keep         = integer(min=0, default=1)
 auto-purge-failures     = boolean(default=yes)
 purge-policy            = option(manual, before-backup, after-backup, default='after-backup')
-post-backup-hook        = string(default=None)
-pre-backup-hook         = string(default=None)
-backup-failure-hook     = string(default=None)
+post-backup-command     = string(default=None)
+pre-backup-command      = string(default=None)
+backup-failure-command  = string(default=None)
 """.splitlines()
 
 class Backup(object):