Fix a bug in Close table and recompiled WindowHelper.dll to .NET 3.5

* Users have reported an issue when running WindowHelper on MI Pro
10.5.2 where it faisl to load the WindowHelper assembly. This assembly
was compiled for .NET 4.0 which wasn't necessary. Recompiled it to .NET
3.5
* Close table from the Layer Control crashes the tools when used on a
thematic layer (issue #5). Has been changed to handle the cosmmetic
layer and a cosmetic layer differently.
- Cosmetic layer is ignored.
- Thematic layer is removed from the map window