Placard contenteditable div support

[kevinparkerson]

Fixes #1612 by allowing contenteditable divs to be used as the .placard-field element in placard. I've made it default to look and behave like a regular input, though you can add data-textarea="true" to the .placard-field element to make it instead look and behave like a textarea.

Additionally, I fixed a bug I noticed with ellipsis for textareas.

Documentation will need to be updated separately.

[interactivellama]

I think the logic is sound. Can you change isDiv to something more descriptive like isContentEditableDiv? And should we check that's it's content editable when create isDiv?
I'm coming from the greenfield of Facades, so any additional comments (especially in the constructor) would be nice.

(a keyCode object map would be nice for readability, too, but that's not what you are in there to add).

[kevinparkerson]

@interactivellama I can change the var name to isContentEditableDiv, though it shouldn't check if it is content editable, b/c if it is disabled on init contenteditable="true" wouldn't be present and the control would think it's a textarea

[interactivellama]

Yeah, you're right. Let's just comment the constructor.
// Placard supports four types of input fields. A <div> that is content editable or an <input>. Either can function as a text field or a text area.