update sources to point to github for moved packages

sources.cfg

 [buildout]
 extends = http://svn.zope.org/repos/main/zopetoolkit/trunk/ztk-sources.cfg
 svn-zope-org = ^
+github = git://github.com/zopefoundation
 
 [sources]
 # Zope2-specific
-AccessControl = svn ${buildout:svn-zope-org}/AccessControl/trunk
-Acquisition = svn ${buildout:svn-zope-org}/Acquisition/trunk
-DateTime = svn ${buildout:svn-zope-org}/DateTime/trunk
-DocumentTemplate = svn ${buildout:svn-zope-org}/DocumentTemplate/trunk
-ExtensionClass = svn ${buildout:svn-zope-org}/ExtensionClass/trunk
-initgroups = svn ${buildout:svn-zope-org}/initgroups/trunk
-Missing = svn ${buildout:svn-zope-org}/Missing/trunk
-MultiMapping = svn ${buildout:svn-zope-org}/MultiMapping/trunk
-nt_svcutils = svn ${buildout:svn-zope-org}/nt_svcutils/trunk
-Persistence = svn ${buildout:svn-zope-org}/Persistence/trunk
-Products.OFSP = svn ${buildout:svn-zope-org}/Products.OFSP/trunk
+AccessControl = git ${buildout:github}/AccessControl
+Acquisition = git ${buildout:github}/Acquisition
+DateTime = git ${buildout:github}/DateTime
+DocumentTemplate = git ${buildout:github}/DocumentTemplate
+ExtensionClass = git ${buildout:github}/ExtensionClass
+initgroups = git ${buildout:github}/initgroups
+Missing = git ${buildout:github}/Missing
+MultiMapping = git ${buildout:github}/MultiMapping
+nt_svcutils = git ${buildout:github}/nt_svcutils
+Persistence = git ${buildout:github}/Persistence
+Products.OFSP = git ${buildout:github}/Products.OFSP
 Products.ZCatalog = svn ${buildout:svn-zope-org}/Products.ZCatalog/trunk
 Products.ZCTextIndex = svn ${buildout:svn-zope-org}/Products.ZCTextIndex/trunk
 Record = svn ${buildout:svn-zope-org}/Record/trunk
@@ -24,8 +25,8 @@ zLOG = svn ${buildout:svn-zope-org}/zLOG/trunk
 ZopeUndo = svn ${buildout:svn-zope-org}/ZopeUndo/trunk
 
 # Deprecated / CMF dependencies
-Products.BTreeFolder2 = svn ${buildout:svn-zope-org}/Products.BTreeFolder2/trunk
-Products.ExternalMethod = svn ${buildout:svn-zope-org}/Products.ExternalMethod/trunk
+Products.BTreeFolder2 = git ${buildout:github}/Products.BTreeFolder2
+Products.ExternalMethod = git ${buildout:github}/Products.ExternalMethod
 Products.MailHost = svn ${buildout:svn-zope-org}/Products.MailHost/trunk
-Products.PythonScripts = svn ${buildout:svn-zope-org}/Products.PythonScripts/trunk
-Products.StandardCacheManagers = svn ${buildout:svn-zope-org}/Products.StandardCacheManagers/trunk
+Products.PythonScripts = git ${buildout:github}/Products.PythonScripts
+Products.StandardCacheManagers = git ${buildout:github}/Products.StandardCacheManagers