Add 'mv' support to RawAccessRequest

In order for an admin user to be able to move files server-side,
RawAccessRequest needed to add a `mv` operation. In addition,
CheckedPath objects need to expose renameTo and moveToDir
methods.
First draft of renaming test
Default command help to fun.__doc__
Refactor prep_directory to fs.py
Refactor rename_fileset to fs.py
Add 'default' argument to proxy_to_instance

In order to produce a lambda which takes just an ID,
a default can now be passed to proxy_to_instance which
will then be used if the proxy string does not contain
the "Class:" prefix as otherwise required.
Add ProxyStringType for use with the CLI
First (non-admin) version of 'rename'

Now `rename Fileset:ID` will rename the OriginalFile.path
fields of a Fileset to match the current template. This
is restricted to the owner of the Fileset for the moment.
FS modification improvements

 * print out all paths to be moved
 * save fileset change in the same transaction
Have 'rename' print out the mv command
test_rename: multi-user integration tests

In order to write the integration tests, we need
to have context objects passed everywhere. This
will also be of use when an admin wants to rename
a fileset for a user.
rename-as functionality
Use raw 'mv' as admin
Fix flake8 whitespace errors
Handle errors on submit(raw)

`fs rename` followed by `fs sets --check` (without
a move inbetween) was leading to a `CmdError` being
printed before this change.
Refactor 'tomove' return to contain target

In preparation for also specifying a tomove for the
log file, we need to specify where the file should
be moved *to*, since the log file is a directory up
from the actual fileset.
Also print CmdError on --move
Move log file as well
Fix flake8 'OK import' err
Remove 'import pdb'