corrected #isEnabled message to have "MCRepository allConcreteSubclasses" return only the usable subclasses (fixes a DNU when using GemTools to add a new repository)
pharo2.0 cannot use the ConfigurationOfOsProcess from http://www.squeaksource.com/MetacelloRepository anymore...
Merge pull request #297 from jbrichau/master

corrected #isEnabled message on MCGitRepository subclasses
Merge branch 'master' into dev