Feature: file management

[OkieLe]

Changes

• File manager
  • Item option menu for both notebook and note
  • Partially refresh on data changes
  • Click item to open editor for both notebook and note(only 1 allowed)
• Notebook editor
  • Show a notebook/note list without sorting
  • Click icon to flip card and show ops menu
  • Ops menu
• Note editor
  • Load note on launch
  • Show title and content from db
  • Send title to preview

[OkieLe]

Some error happened on merge, just close it.