Add menu item - Display Field Model

[ShuhaoBai]

User can select this menu to display field network model again if they moved to some other menu display.

[ShuhaoBai]

Added the menu item for Display Field mode in this commit d792017

[ShuhaoBai]

Fixed the issue of switching between menu items crashes topo rendering. Plz see 4c428dd

[ShuhaoBai]

This issue is included in #452