Reducing use of FAKE

[dsyme]

@baronfel's comments on why this repo is using FAKE:

The big thing we need FAKE for at this point is doing text-replacement on the FsLibLog dependency. There are two paths to removing this need:

• implement contentFiles text-templating support in Paket to align with nuget specs here, then ship FsLibLog as a nuget package instead of a raw file reference in Paket (issue already exists, just needs implemented)
• do the packaging described above anyway, and move off of Paket (we're not a big fan of this step)
• create/find a msbuild task/target to do the replacement in a more regular way as part of the build pipeline

In other repos we've moved to using the FAKE libraries in a build.fsproj, so we'd likely do that here for ease of use/consistency.