Major updates: Add real-time config center / Add JSON APIs

Recommendation Index: ⭐⭐⭐⭐

BUG Fixes

• Form delete hook API error
• Permission check error [Seriously]
• HTMLFile/HTMLFiles APIs of engine
• Table export error
• Asset response content-type error
• Form selection ajax load data error

Improvement

• Add post/delete result to hook APIs
• Add permission check to table custom buttons
• Add missing translate
• Add footer theme info
• Support copy info fields to detail
• Add a real-time config center
• Add FieldFilterOptionsFromTable API
• Add new form component -- code
• Add schema support to Postgres
• Add theme version check
• Add global site offline flag check
• Add admin JSON APIs
• Improve language module
• Add new action File Upload Action
• Improve link, support no-pjax jump
• Add new API SetFilterFormInputWidth/SetFilterFormInputWidth
• Add database check
• Add notify when login overdue
• Add BasePlugin make the plugin easier to implement
• Change panel title/description type to template.HTML