Lots of cleanup/bug fixes around handling
New file appears unsaved
Throw task cancelled exception when save cancelled
Adding UI tests
Missed private CanSaveDocument
Switched over to delegate commands for a heap of commands on shellviewmodel
Markpad now knows about 'attached' images when opening a document
More scenarios around saving as when there are associated images
Added some document editor behaviour UI automation
More UI tests
Fix an error that causes startup crash with "NullReference" exception

The issue:
if the code
openSubKey.GetValue("") returns null, then the startup failes with
NullReference exception.
The fix:
Adding null check before calling ToString method on the return value
Make previous fix even more robust
Merge pull request #348 from imgen/master

Fix startup crash issue with a NullReference exception
Updated to released version of White
Updated readme
Merge pull request #349 from JakeGinnivan/ReadmeUpdate

Updated readme
Fixed open existing document looking like it had been modified
Removed a delay put in to resolve a bug
Merge pull request #346 from JakeGinnivan/DocumentSourceFilesCleanup

Document source files cleanup
Fixed an issue where IOExceptions were being thrown (and caught by the generic exception handler which spawned a new window) when in 'directory watcher' mode, when a file was being created.

ie, I'd save a file in photoshop, it'd create a stub file, markpad would throw exception, then photoshop would actually write to it.