MWBlockImage new DOM fixes

MWBlockImage
* Remove properties which just cache model properties. We can get
  fresh values from the model whenever needed and this just causes
  problems keeping them in sync.
* Tidy up DOM documentation indentation
* Merge setupCaption and setCaptionVisible into updateCaption. The
  caption's visibility can be calculated inside the method from
  model attributes.
* No need to generate figcaption on init, updateCaption  will do
  this for us
* Storing full view and model in this.caption is unnecessary,
  just store this.$caption (view.$element) and this.captionVisible
* Append the caption directly to the figure now there is no container
* Simplify setCaptionVisible
* Add in fix to account for border to figure width
* updateSize can get values from the model if they are not provided
* Remove unnecessary styles being set on this.$element.

MWImageCaption
* Generate as a figcaption instead of a div for direct attachment

MWImage
* Missing docs

CSS
* Cleanup reset styles, remove redundant add in required
* Fix margins for left/right floats to match .tleft/.tright
* Use more specific selector for inner border (thumbimage) to avoid
  matching shields.
* Remove unnecessary frameless styles, it has no border by default.

Change-Id: I52e0e10b465bb9761c2e4be28c98bec37b0dd2ca
Merge "MWBlockImage new DOM fixes"