Fixes Template.ToXml() (U4-3508) and refactored Template.Import to use PackagingService.ImportTemplates.

Fixed nullreference bug in ImportTemplates when used with XElement("Template"). (Added test for case with one template only)
Merge pull request #246 from lars-erik/6.2.0-fix-U4-3508

Fixes Template.ToXml() (U4-3508) and refactored Template.Import to use P...