[#1] Minor typo in parser
[#1] Handle RDF parsing errors

Refactored the parsing code so it can raise a single RDFParserException
which can be catch higher up, eg on the harvester.
[#1] Support multiple profiles on the RDF Parser

Big refactor to support multiple profiles when aprsing RDF graphs for
datasets. Basically, there is only one parser class which can be
initialized with different profiles.

These are classes inheriting from a base RDFProfile, and registered on
setup.py. They implement a `parse_dataset` method which get called by
the parent parser class on each of the registered profiles.
Merge branch 'master' of github.com:okfn/ckanext-sweden