make cron task configurable

conf/app.ini

@@ -281,21 +281,34 @@ DRIVER =
 ; Based on xorm, e.g.: root:root@localhost/gogs?charset=utf8
 CONN =
 
+[cron]
+; Enable running cron tasks periodically.
+ENABLED = true
+; Run cron tasks when Gogs starts.
+RUN_AT_START = false
+
+; Update mirrors
+[cron.update_mirrors]
+SCHEDULE = @every 1h
+
+; Repository health check
+[cron.repo_health_check]
+SCHEDULE = @every 24h
+; Arguments for command 'git fsck', e.g.: "--unreachable --tags"
+; see more on http://git-scm.com/docs/git-fsck/1.7.5
+ARGS = 
+
+; Check repository statistics
+[cron.check_repo_stats]
+RUN_AT_START = true
+SCHEDULE = @every 24h
+
 [git]
 MAX_GIT_DIFF_LINES = 10000
 ; Arguments for command 'git gc', e.g.: "--aggressive --auto"
 ; see more on http://git-scm.com/docs/git-gc/1.7.5
 GC_ARGS = 
 
-; Git health check.
-[git.fsck]
-ENABLE = true
-; Execution interval in hours. Default is 24.
-INTERVAL = 24
-; Arguments for command 'git fsck', e.g.: "--unreachable --tags"
-; see more on http://git-scm.com/docs/git-fsck/1.7.5
-ARGS = 
-
 [i18n]
 LANGS = en-US,zh-CN,zh-HK,de-DE,fr-FR,nl-NL,lv-LV,ru-RU,ja-JP,es-ES,pt-BR,pl-PL,bg-BG,it-IT
 NAMES = English,简体中文,繁體中文,Deutsch,Français,Nederlands,Latviešu,Русский,日本語,Español,Português do Brasil,Polski,български,Italiano