add indexing of datasets whilst harvesting
Fix bug in harvest job reports
Merge branch '2.0-dataset-sources' of github.com:okfn/ckanext-harvest into 2.0-dataset-sources
fix gather_stage if there is a previous job

change check on gather stage to check for changed packages since
last job instead of current harvest job's gather_start

fix attribute look up bug

fix print_job to print 0 gather_errors instead of key error
Merge branch '2.0-dataset-sources' of github.com:okfn/ckanext-harvest into 2.0-dataset-sources
Refresh session after each harvest stage

Otherwise the eg the source config got cached and you needed to restart
the consumers to refresh it.
Add XML declaration to contents if not present
fix print gather_errors
Merge branch '2.0-dataset-sources' into source_extra_config_validation