Make it more obvious when a macro placeholder is included in a text selection

When a macro is part of a user's selection in the editor, it should be more obvious that it has been selected.

These are the ways that a macro could become part of a user's selection in the editor:

• Click the header of the body macro placeholder,
• Click the "Select for Copy / Cut" option in the properties panel,
• Use the keyboard arrows + shift key to select a range of text, or
• Use the mouse to click and drag a range of text

The visual distinction between a macro that's selected in the editor can be quite vague across browsers.

Each browser (Chrome, IE, FF) does a decent enough job of inline placeholders. Because inline placeholders are images, the browser is familiar with how to place a selection indication over the top of them.

The browsers operate a bit differently for bodied macro placeholders:

• Chrome (OSX) highlights the entire body contents of the macro, including vertical padding (but not horizontal).
• Firefox (OSX) will apply a glowing outline to the inside of the bodied section of the macro placeholder. The glow is similar to that applied to form input fields.
• IE (7,8) provides no indication that the macro placeholder is selected. IE only highlights text characters in the editable region.