Add DialogShower Factory class

Spawns dialog windows and returns their viewmodels
Merge branch 'master' of github.com:IMDC/LiveDescribe-Desktop into valdev

Conflicts:
	LiveDescribe/LiveDescribe/ViewModel/DescriptionInfoTabViewModel.cs
audio canvas and description canvas get disabled when playing video

removed uneeded file LiveDescribe/Model/Video.cs
Add IDescribableInterval, Rename Text Properties
description gets selected in list when it is playing

added new event in mainwindowviewmodel OnPlayingDescription
Fix issue with naming Description Files

AudioFiles now correspond to their proper locations
Merge branch 'master' into danieldev

Conflicts:
	LiveDescribe/LiveDescribe/ViewModel/MainWindowViewModel.cs
deletes unused description files when closing a project