Don't store element attributes in media tokens that otherwise could be generated from the token or the file entity itself

Problem / Motivation

A lot (maybe all) of the information in the attributes structure can be generated based on other information in the macro or from the file entity or file settings. This is how the $tag_info['attributes'] structure might look like after media insertion into the text area, in json format:

{
  "attributes":{
    "alt":"Overridden Alt text",
    "title":"Overridden Title text",
    "height":220,
    "width":148,
    "class":"media-element file-teaser media-wysiwyg-align-left",
    "data-delta":"1"
}

Proposed resolution

Generate the attributes based on information from the macro or file entity itself during input filtering, and omit inserting these in javascript:

• The alt and title attributes should be generated based on the values in $tag_info['fields'] and the Drupal.settings.media.img_alt_field and Drupal.settings.media.img_title_field settings.
• The height and width attributes should not be set if they differ from the selected style/image. It also causes problems when selecting a different format in the wysiwyg media browser. If necessary, add this information in the input filter.
• All inserted classes can be generated based on other values in the media token: "type":"media" → media-element, "view_mode":"teaser" → file-teaser, "fields"."alignment":"right" → media-wysiwyg-align-right