fixup! Add referred parts' hash strings in __buildout_signature__, that...

fixup! Add referred parts' hash strings in __buildout_signature__, that invokes rebuild of a part when one of its (recursive) dependencies are modified.

egg signatures are always {egg_name}-{egg_verson}, there should not be a "egg" prefix for setuptools

zc.recipe.egg_/src/zc/recipe/egg/api.rst

@@ -104,7 +104,7 @@ computed by the egg recipe by looking at .installed.cfg:
     <BLANKLINE>
     [sample-part]
     __buildout_installed__ = 
-    __buildout_signature__ = sample-... setuptools-...egg zc.buildout-... zc.recipe.egg-...
+    __buildout_signature__ = sample-... setuptools-... zc.buildout-... zc.recipe.egg-...
     _b = /sample-buildout/bin
     _d = /sample-buildout/develop-eggs
     _e = /sample-buildout/eggs