Removed the FSharp.Core reference from the Facio.BuildTasks project. We're not using any functionality from FSharp.Core in there anyway, and it allows us to implement a solution for the assembly-resolution issue which arises at build-time on some systems.
Implemented an assembly resolver helper which gets installed whenever one of the build task classes are created; this fixes the crash on some systems were FSharp.Core 4.0.0.0 wasn't found (it's needed by ExtCore) because binding redirects aren't applied by MSBuild.