Standardize Alternate Text label

Panopoly is inconsistent in how it names alt text fields.

Since Media (#1 below) uses "Alt Text," and it's a bit harder for us to change that, this would be the easiest label to standardize on. IMO "Alternative Text" is friendlier, but to do that we'd have to form_alter the media forms and that probably isn't worth the maintenance cost.

Here are some of the variations:

1. Create a new page and in the WYSIWYG (TinyMCE) choose Add Media. Upload (or select existing) image. Here you see:

<label for="edit-field-file-image-alt-text-und-0-value">Alt Text </label>
<input class="text-full form-text" type="text" id="edit-field-file-image-alt-text-und-0-value" name="field_file_image_alt_text[und][0][value]" value="" size="60" maxlength="255">

2. Create a new page and add a Featured Image. Here you see:

<label for="edit-field-featured-image-und-0-alt">Alt Text</label>
<input type="text" id="edit-field-featured-image-und-0-alt" name="field_featured_image[und][0][alt]" value="" size="60" maxlength="512" class="form-text">

3. Go to an existing page and click Customize this Page (at bottom). Add a new pane. Click add image. Choose an image and upload it. Here you see:

<label for="edit-field-basic-image-image-und-0-alt">Alternate text </label>
<input type="text" id="edit-field-basic-image-image-und-0-alt" name="field_basic_image_image[und][0][alt]" value="" size="60" maxlength="512" class="form-text">