Layertree ux

[pgiraud]

These commits include an example for the CGXP LayerTree widget.
This was a good point to start with to fix visual issues in IE and to add some UX enhancements.

[asaunier]

I have no special comments about the code changes. They look OK.

I have made a few tests in a real project with various browsers (FF9, Chrome, Safari 5.1, IE7-8-9):

• A bug that is not new and occuring with all browsers: when moving up or down a layergroup, the background layer is switched back to the default one (or the first one in the combo?).
• With FF, Safari and Chrome, I have noticed no glitch. The new layout of the layergroups is really excellent! Thanks! It's a pity that IE versions do not support those improvements.
• With IE I have noticed two problems with the layer opacity slider:
• IE7 + IE8: the layer opacity is not always correct when playing with the opacity cursor: for instance the layer items seem darker on the map when slider value is 99% than 100%
• IE7 + IE8 + IE9: when playing with the slider cursor, the layer visibility sometimes switches to false (layer disappears) when sliding back to 100%.

Anyway good job! :)

[elemoine]

Where do we stand with this pull request?

I also see that this pull request makes changes to the core css. Is this wanted?

[sbrunner]

Otherwise it seem good => merge.

[elemoine]

@pgiraud is this good to merge now?