Rename "repo_type" attribute of the repositories scope to "type"

When the scope was initially implemented we were running on Ruby 1.8 and
"type" conflicted with Object#type so we had to name the attribute
differently. Since we're only supporting Ruby 2+ now "type" can be used
instead.
Merge pull request #54 from SUSE/review_140808_rename_repo_type_to_type

Rename "repo_type" attribute of the repositories scope to "type"