Add "More" button to ModelMenuPanel
Renamed ModelMenuPanel ActionButtonPanel

It's more descriptive, I hope.
Remove ModelMenuPanel
Rename ActionButtonPanel event handlers
Remove old ModelMenuPanel event handlers
Set up menu for "More" button

This includes an event handler to show the menu, and some basic
styling. Currently, the menu holds dummy items.
Move handler for "More" button to ActionButtonPanel

Remove ActionButtonPanelMoreHandler.
Use Font Awesome fixed-width icons

They align nicely in menus.
Remove rounded corners from ActionButtonPanel buttons
Finish adding "More" button actions

Move buttons from ActionButtonPanel to MoreActionsMenu.
Updates to display of items in MoreActionsMenu