Add a Description field to menu settings options

Problem/Motivation

Content managers in certain spaces, such as Education, need to provide descriptions for menu items for accessibility reasons. Asking a content manager to create menu items through menu settings and to set descriptions through the menu administration area is not very user friendly.

Proposed resolution

Provide a description field in the menu settings section that will set the menu link's title tag.

Remaining tasks

Review needed on the attached patch.

User interface changes

Description field provided in the menu settings section of the node/add and node/edit forms.