OPENUCB-340: Improve ability to edit node content in a panel

Does the following customizations to panopoly_widgets:

1. For existing text widgets, in the Settings modal, add a Link to the appropriate place to find revisions
2. For node content (via Add Content Item), in the Settings modal, add a Link to the node that also identifies the node number
3. For node content (via Add Content Item), in the Settings modal, "Display Settings," only Allow "Content" (remove "Fields" and "Table")
4. For node content (via Add Content Item), in the Settings modal, for "Content Settings," default to "Full Content" instead of "Teaser"