wendelin.core: Don't forget to set :egg for wendelin.core-dev too

In 2d7e6179 (wendelin.core: Add part/recipe how to build it from git
repository) I've added wendelin.core-dev part, but forgot to set :egg
variable inside it.

Reviewed-by: Trust-me

component/wendelin.core/buildout.cfg

@@ -13,6 +13,7 @@ egg = wendelin.core
 # wendelin.core installed from latest git version
 [wendelin.core-dev]
 recipe = zc.recipe.egg:develop
+egg = wendelin.core
 setup = ${wendelin.core-repository-submoduleinit:location}