Implemented SCP support

Implemented:
- recursive up/down
- preserve times (download only)

Missing:
- wildcards
- xattrs
- preserve times (upload)
Add tests for scp
Fix bug in scp

When uploading a file with a linefeed in the first few bytes, scphandler
would crash. Now it wont.
s/argparse/optparse/g

Substitute argparse for optparse to support python 2.6.
Also moved the argument parser to class level.
Move scp to a non-threaded model.
set the executable flag
fixed some typos, wording
use a constant for the chunk size in r/w operations
minor formatting
catch invalid sizes
expand variable name
catch errors when sending the status and closing the channel
added elif
typo
test unicode, support for spaces in names
catch stat errors and translate them to SCPException
optparse.OptionParser is not thread-safe, use a different instance per process
options not implemented
removed unused imports
set scp timeout (default to 30 secs)