This looks like a big patch, but it's very straightforward: no
behavior has changed.
After the umpteenth time spent hitting a compile error because I
passed a `FilePath` rather than a `File` to `readBlobFromPath`, I
decided to finally make the needed refactors to Semantic.IO, and to
split off the `File` type and `Files` effect. This patch:
* adds the `MonadIO` class to `Prologue`'s export list
* moves `File` into `Data.File`
* moves `Handle` into `Data.Handle`
* moves `Files` into `Semantic.Task.Files`
* moves functions for reading blobs into `Data.Blob`
* keeps general IO helpers in Semantic.IO
* renames `readFile` to `readBlobFromFile`
* renames `readBlobFromPath` to `readBlobFromFile'`
This should have a positive effect on compile times and ease of
navigation throughout the codebase.
