Subcourse for 2.7

Hi, Matt. I have found that your version of submpdule plugin have some extra features, that does not have David's version, but it's much more far from current 2.7 version, than David's. I have taken all significant features of your version and rebased it on latest version, so you can take this changes and merge your module into original branch. I have send pull request to David, but i did not included in pull request for him parts for qualification module, because i cannot found it in moodle plugin repository. Maybe you decide to publish qualification module in repository and to send pull request to David (in pull request i'm sending to you qualification module is included)