Generate <figure> and <figcaption> when an image has a caption

[stcarrez]

When an image has a caption, we should generate a <figure> and a <figurecaption>

Example for dotclear:

((https://test.com/photo.jpg|Photo|C|Photo long description))

we should have:

<figure class="wiki-img-center">
  <img src="https://test.com/photo.jpg" alt="Photo" />
  <figcaption>Photo long description</figcaption>
</figure>

And for Mediawiki:

[[Image:study_current_measure1.png|thumb||left|Current Measurement]]

We could have:

<figure class="wiki-img-thumb wiki-img-left">
  <img src="study_current_measure1.png" alt="Current Measurement" />
  <figcaption>Current Measurement</figcaption>
</figure>