Calculate the line-height when typeGap is changed.
1. Bug fix: Layout of grids at custom typeGap.
1. Update a display value of the line-height in the setting-dialog.
1. Re-order items in the setting-dialog.
1. A value of typeGap is stored per instances are show or hide.
1. Extract a module 'SettingDialog'.
1. Extract a module 'EditMode'.
1. Refactor the LayoutManager.