make active current model in the navigation

[nad2000]

• expands the currently selected application nav-items;
• marks the current model - active;
• adds the link to the application index (app_index).

[nad2000]

• expand the currently selected application nav-items;
• mark the current model - active;
• added the link to the application index (app_index).

[app-generator]

Ty @nad2000 for your contribution.