add meterpreter side of stdapi.fs.file.mv

Adds MoveFile and rename to Windows and POSIX Meterpreters respectively.
Tested in windows x86 and x64 against Win7 and 2008r2.
```
Testing:
(Local): "touch /tmp/testfile"
Open meterpreter session
"upload /tmp/testfile ."
"mv testfile renamed_file"