Import EpiCollect Plus datasets. Refs #424
Unit Tests #Refs 424
Include SoundCloud template. Refs #424

This commit adds the SoundCloud template (presenter and importer) to fix
the layout in the importer section.
Docs for new EpiCollect Importer. Closes #424
Merge pull request #426 from PyBossa/issue-424-epicollect

Issue 424 epicollect