Removed "." ApplicationIcon setting in Heapshot.Reader project that was causing build error.
Fixes to get heapshot.gui compiling in VS2012 and with gtk-sharp 2.12.

- Bumped target frameworks to 4.0 to work with gtk-sharp 2.12
- Set all projects to output their binary into common "..\bin" solution directory.
- Set CPU to x86 for compatibility with gtk-sharp 2.12 on 64-bit systems