[w2llatexform][w2lonpdf] Style changes. CSS id and class added. …

_(this is the copy of last commit message)_

New CSS: _#w2lFmFormer_ is the id of the form in the _w2llatexform_ page and
_.w2lLogOutput_ is the class of the textareas in the _onpdf_ page.
There is no defined style for those elements, their CSS code must be written
in a skin of the wiki.

Added two messages:
- _wiki2latex_version_ which shows the extension name with its version.
- _wiki2latex_version_tag_ shows the extension name between the passed
parameters. The first one is meant to be the opening tag and the other the
closing tag. This allows to write (e.g.) "&lt;a href="site.com"&gt; Wiki2Latex
&lt;/a&gt; (W2L_VERSION)".