appbuilder init hybris creates missing WP8ProductID and WP8PublisherID properties

Fixes http://teampulse.telerik.com/view#item/276029
Extract guid creating into a dedicating helper function
Merge pull request #468 from Icenium/totev/fix-init

appbuilder init hybrid creates missing WP8 properties
Add ability to select a particular avd for $ appbuilder emulate android

Implements http://teampulse.telerik.com/view#item/276157