archipelago: Change posixfd_signal_desc structure

Change signal_file field in posixfd_signal_desc structure to
reflect libxseg changes.
archipelago: Fix bug in restart() function

Add missing comma in stop() function.
Merge pull request #21 from cnanakos/develop

Python fixes
filed: Add support for Pithos object migration

Pithos places its objects under the hexlified hash of the contents. It also
creates the dir hierarchy according to the first 6 characters of the object
name. In contrast, filed hashes the object name to get 6 random characters for
the dir hierarchy. In this commit, we introduce a fallback path for filed to
find objects created by Pithos and move them to the directory expected by filed.
filed: Split dir creation

Split dir creation into a different function. Also avoid looping around mkdir.
filed: Do not create dirs when doing read I/O
filed: Add migrate flag

Add a boolean migrate flag, to enable migrations of pithos objects to their new
locations.
python: Fix vlmc list with filed
python: Fix typo error
Merge pull request #22 from philipgian/feature-filedfix

Fixes for filed <-> pithos integration
Docs: Describe archipelago open/close mechanism
docs: Update archipelago packages

Update archipelago packages and installation procedure.
docs: Update archipelago config section
docs: Add archipelago v0.4 upgrade notes
docs: Remove numbers from sections
docs: Fix design doc index
docs: Update garbage collection design doc
docs: Separate install and admin's guide

Separate installation and administrator's guide.
Also include minor documentation fixes.
docs: Update administration_guide
archipelago: Add info when retrying to get a lock