Create algebras for FileSystem

[mr-calvert]

The most pressing need here is for the ability to convert Strings to Path instances while tagging them with appropriate FS dependent D domain types. This issues can be closed with just enough work to create FSPath.P[JVMA, ?] instances where ? relates uniquely to a specific filesystem.

There's a lot more meat to the FileSystem interface though, so wrapping more of it would be nice.