Updates for new FCPath

[rfrenchseti]

• Fixes Update hosts to use filecache #143
• Fixes Update tests and spicedb to use filecache Path-like functionality #144
• Fixes Modify oops and hosts to use filecache FCPaths when they are implemented #145

Major changes:

• Change gold master tests to use new FCPath functionality from the filecache package. This returns much of the code to the way it looked before PR Changes to support rms-filecache #138 and makes the code easier to read.
• Change all hosts to accept an FCPath as the argument to from_file and from_index. If the provided path is remote, the file is retrieved before use.
• Change spicedb to use FCPath.

Issues:

• Due to the lack of sufficient tests, most of the changes to the hosts modules have not been tested.

[jnspitale]

All units tests pass, looks nice. Only comment I have is really about filecache: I see file retrieval is done explicitly. It seems like this could be hidden inside the class, where the local path is stored inside the class instance and retrieval would be performed if the local path is not yet defined.

[markshowalter]

I will need to gain some experience with the new module, but I see no problem with your changes. Go ahead and merge.