add deletion to ckan harvester
[#67] add manage_deletion config

remove utf decode and clean up code
[#67] delete based on guid
[#67] clean up code, add documentation for manage_deletions
[#67] clarify manage_deletion documentation
[#67] change guid to package_id in HarvestObject deletion creation
Merge remote-tracking branch 'upstream/pr/67' into support-for-old-ckans

Conflicts:
	README.rst
Merge branch 'master' into support-for-old-ckans