Fix default_opts merging when creating new Project

Merging of default_opts with params actually didn't work correctly. Without this fix the merged params
have mixed string and symbol keys:

Merged params {:issues_enabled=>true, :wiki_enabled=>true, :wall_enabled=>false, :snippets_enabled=>false, :merge_requests_enabled=>true, :public=>false, "name"=>"test1", "path"=>"", "import_url"=>"", "description"=>""}

(this was actually cut-n-pastet from the debug log after adding 
     ::Rails.logger.debug "Merged params #{default_opts.merge(params)})
in create_context.rb:22