Network.URI now correctly chosen from network or network-uri

In network-2.6 the Network.URI module was split off from the network
package into the network-uri package. This commit means that rdf4h
automatically gets Network.URI from the right package. See the
documentation at:
http://hackage.haskell.org/package/network-uri

Fixes robstewart57/rdf4h#14
Added network-uri predication on executable and testsuite
cabal version fix to 1.2.7
deprecating `sortTriples` and `removeDupes`; introducing `uniqTriplesOf`
Attributes Slava Kravchenko in cabal file
refactored `rdfCollectionToList`
Merge pull request #3 from robstewart57/w3tests

It works nicely! Thank you!
Merge pull request #4 from robstewart57/cordawyn-attribution

Attributes Slava Kravchenko in cabal file
stub non-matching patterns in W3C tests
minor clean-up
Merge branch 'master' into w3tests
Streamlined quickcheck tests by removing duplication

All tests are now defined in Data.RDF.GraphTestUtils.hs . New graph
implementations only need to provide implementations of

empty'     :: RDF rdf => rdf
mkRdf'     :: RDF rdf => Triples -> Maybe BaseUrl -> PrefixMappings -> rdf
triplesOf' :: RDF rdf => rdf -> Triples

See Data.RDF.MGraph_Test.hs for an example. Add your graph
implementation to `defaultMain` in Test.hs .
Merged cordawyn/master
moved `resolveQName` and a few other functions to `Data.RDF.Types`
resolveQName returns a Maybe value instead of immediately failing when
unable to look-up the prefix
refactored t_qname
Uses isAbsoluteURI from network-uri package

The rdf4h isAbsoluteUri uses isAbsoluteURI from network-uri, and this
function is moved to Data.RDF.Types . Fixes robstewart57/rdf4h#18 .
adds ghc-prim build dependency for ghc < 7.6. Fixes robstewart57/rdf4h#13
Fixed regression introduced in edaaee283e3bbfd9af36dec3eaf67452472a0448

The correct function in Network.URI is `isURI`, which is documented
thus:

> "Test if string contains a valid URI (an absolute URI with optional
fragment identifier)."

RDF URIs are optionally appended with fragments e.g. `#foo`. The
edaaee283 commit incorrectly opted for `isAbsoluteURI`, which is not
the same as RDF URIs given the following haddock documentation:

> "Test if string contains a valid absolute URI (an absolute URI without
a fragment identifier)."

Also, this identified a new problem in the turtle parser tests from
`data/ttl/example7`, which includes "ns10:Édimbourg" in the parsing
test.

URIs conform to RFC3986 which does not support unicode, i.e. the É
symbol. IRIs conform to RFC3987 which includes unicode. The rdf4h
library does not include IRIs, only URIs, hence this unit test has
been disabled. See:

https://tools.ietf.org/html/rfc3986
https://tools.ietf.org/html/rfc3987
implemented `expandTriples`