fixes #490
fixes #490
update version info for release 1.8.3.1
Merge branch 'release_v1.8' into dev-1.8

Conflicts:
	PowerPointLabs/PowerPointLabs/PowerPointLabs.csproj
	PowerPointLabs/PowerPointLabs/Ribbon1.cs
	PowerPointLabs/PowerPointLabs/ThisAddIn.cs
resolves some merge conflicts
Added context menu icons for shapes lab
using mockup message box to capture user's closing option
fixes #491, more stable mock up save dialog
Merge branch 'master' into dev-1.8
Add icon for Add To Shapes Lab option in context menu
Merge branch 'dev-1.8' of https://github.com/PowerPointLabs/repo into dev-1.8

Conflicts:
	PowerPointLabs/PowerPointLabs/PowerPointLabs.csproj
	PowerPointLabs/PowerPointLabs/Properties/Resources.Designer.cs
	PowerPointLabs/PowerPointLabs/ThisAddIn.cs