Added expat package 2.1.0

Also added a basic script to download sources using uscan,
and prepare orig tarball (due to Quilt 3.0 sources format)
Merge pull request #12 from sbadia/expat

Added expat package 2.1.0
Added lxml package 3.3.1

Provide PPA packages:

* python-lxml pythonic binding for the libxml2 and libxslt libraries
* python-lxml-dbg pythonic binding for the libxml2 and libxslt libraries (debug extension)
* python-lxml-doc pythonic binding for the libxml2 and libxslt libraries (documentation)
* python3-lxml pythonic binding for the libxml2 and libxslt libraries
* python3-lxml-dbg pythonic binding for the libxml2 and libxslt libraries (debug extension)

Depends to
https://github.com/Juniper/contrail-third-party-packages/pull/12 for
upstream/debian/utils/get-sources.sh script.