Added Eclipse tutorial to site

Added "Eclipse step by step guide" to
http://www.gwt-openlayers.org/user-reference.html

Added link to showcase in topbar

Added binary downloads
additions for transition effects, enhanced enum and extended GridLayer to reflect OpenLayers API at http://dev.openlayers.org/docs/files/OpenLayers/Layer/Grid-js.html#OpenLayers.Layer.Grid.transitionEffect.
Merge pull request #3 from sebasbaumh/transitioneffects

additions for transition effects