Added functionality to allow Org admins to export their org's templates. ...

Re-used the template_export templates template_export.docx.erb
and template_export.pdf.erb.

Changes:
 - Moved templates template_export.docx.erb and template_export.pdf.erb
to a separate view folder template_exports.
- Added functionality for Org admins to export both current and historic
templates for their organisation. The version name has been appended to
the templates, e.g., My_Template_v0.docx or  My_Template_v5.pdf.

Fix for issue #2091.