Upgrade solution from F# 2.0 + VS2010 to F# 3.1 + VS2013

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This is a prerequisite to issue 89 (adding support for .NET 4.5 and SL5).

We'll need to:
1) Upgrade the solution and projects
2) Address any F# 3.0 breaking changes
3) Drop the SL4 projects (which are no longer supported; we will replace with 
SL5 support, see issue 89)
4) Adapt the build scripts (perhaps taking the opportunity to move away from 
.bat scripts, see issue 74)

Original issue reported on code.google.com by stephen....@gmail.com on 31 Mar 2013 at 3:52