If the newly created project is prior to .NET 4.5, set Platform to x86 instead of AnyCPU (32-bit preferred)

Otherwise the compiled program will not run
Show AnyCPU 32-bit preferred only if the opened project targets .NET 4.5
Merge pull request #50 from linquize/prefer32-bug

AnyCPU 32-bit Preferred should only be available for .NET 4.5 projects
Merge pull request #49 from ssarangi/master

Make members in LineNumberMargin protected so derived classes can specialize it and still use the same typeface, emSize & maxLineNumberLength