Add database.type to config file

We add a database type, which is defaulted to sqlite

config.yaml

@@ -20,9 +20,10 @@ web:
     frontend:
       path: /opt/fasten/web
 database:
-  location: '/opt/fasten/db/fasten.db'
+  type: 'sqlite' # postgres also supported, but still experimental changes
+  location: '/opt/fasten/db/fasten.db' # if postgres, then host=localhost user=gorm password=gorm dbname=gorm port=9920 sslmode=required TimeZone=Asia/Shanghai
 log:
-  file: '' #absolute or relative paths allowed, eg. web.log
+  file: '' # absolute or relative paths allowed, eg. web.log
   level: INFO
 jwt:
   issuer: