Chat Redesign:
+ Skin support.
+ New 'ChatSkin' instance parameter, with currently two possible values: 'classic' and 'bubbles'.
+ Skins are located in the new packages/xowiki/www/resources/chat-skins/ directory.
+ New 'bubbles' skin, default for the chat package.
+ Old skin renamed to 'classic', default for the xowiki includelet.
+ New skins can be created by just adding the css and js files in the skins directory, and naming them accordingly. For example, being '$skin' the name of the new skin, the files should be named chat-$skin-common.js and chat-$skin.css.
+ New '-skin' parameter to the Chat login proc, containing the name of the skin (i.e. 'classic' or 'bubbles').
+ Bump version number.